Cisco Intrusion Prevention System Device Manager Configuration Guide for IPS 7.3

Signature Definitions Pane

In the Signature Definitions pane, you can add, clone, or delete a signature definition policy. The default signature definition policy is called sig0. When you add a policy, a control transaction is sent to the sensor to create the policy instance. If the response is successful, the new policy instance is added under Signature Definitions. If the control transaction fails, for example because of resource limitations, an error message appears.

If your platform does not support virtual policies, this means you can only have one instance for each component and you cannot create new ones or delete the existing one. In this case, the Add, Clone, and Delete buttons are disabled.

Signature Definitions Pane Field Definitions

The following fields are found in the Signature Definitions pane:

• Policy Name—Identifies the name of this signature definition policy.
• Assigned Virtual Sensor—Identifies the virtual sensor to which this signature definition policy is assigned.
• Applied Threat Profile—Identifies the threat profile that has been applied to the signature definition policy.

Add and Clone Policy Dialog Boxes Field Definitions

The following field is found in the Add and Clone Policy dialog boxes:

• Policy Name—Lets you create a unique name for the new policy.

Adding, Cloning, and Deleting Signature Policies

To add, clone, or delete a signature definition policy, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions , and then click Add .

Step 3 In the Policy Name field, enter a name for the signature definition policy.

Step 4 In the Threat Profile field, choose one of the following threat profiles from the drop-down menu:

– SCADA—Default signature set plus SCADA-specific signatures, that is, signatures for protecting Industrial Control Systems (ICS).

– Edge—Default signature set plus signatures that help in securing an Internet connection.

– Web_Applications—Default signature set plus signatures for protecting web server farms.

– Data_Center—Default signature set plus signatures for protecting data centers.

Tip To discard your changes and close the Add Policy dialog box, click Cancel.

Step 5 Click OK . The signature definition policy appears in the list in the Signature Definitions pane.

Step 6 To clone an existing signature definition policy, select it in the list, and then click Clone . The Clone Policy dialog box appears with “_copy” appended to the existing signature definition policy name.

Step 7 In the Policy Name field, enter a unique name.

Tip To discard your changes and close the Clone Policy dialog box, click Cancel.

Step 8 Click OK . The cloned signature definition policy appears in the list in the Signature Definitions pane.

Step 9 To remove a signature definition policy, select it, and then click Delete . The Delete Policy dialog box appears asking if you are sure you want to delete this policy permanently.

Step 10 Click Yes . The signature definition policy no longer appears in the list in the Signature Definitions pane.

Signature Configuration Field Definitions

This section lists the field definitions for configuring signatures, and contains the following topics:

• Sig0 Pane
• Add, Clone, and Edit Signatures Dialog Boxes
• Edit Actions Dialog Box

Sig0 Pane

The following fields are found in the Sig0 pane:

• Filter—Lets you sort the list of signatures by selecting an attribute to filter.
• ID—Identifies the unique numerical value assigned to this signature and subsignature. This value lets the sensor identify a particular signature.
• Name—Identifies the name assigned to the signature.
• Enabled—Identifies whether or not the signature is enabled. A signature must be enabled for the sensor to protect against the traffic specified by the signature.
• Severity—Identifies the severity level that the signature will report: High, Informational, Low, Medium.
• Fidelity Rating—Identifies the weight associated with how well this signature might perform in the absence of specific knowledge of the target.
• Base RR—Displays the base risk rating value of each signature. IDM automatically calculates the base risk rating by multiplying the fidelity rating and the severity factor and dividing them by 100 (Fidelity Rating x Severity Factor /100). Severity Factor has the following values:

– Severity Factor = 100 if the severity level of the signature is high

– Severity Factor = 75 if severity level of the signature is medium

– Severity Factor = 50 if severity level of the signature is low

– Severity Factor = 25 if severity level of the signature is informational

• Signature Actions—Identifies the actions the sensor will take when this signature fires.
• Type—Identifies whether this signature is a default (built-in), tuned, or custom signature.
• Engine—Identifies the engine that parses and inspects the traffic specified by this signature.
• Retired—Identifies whether or not the signature is retired. A retired signature is removed from the signature engine. You can activate a retired signature to place it back in the signature engine.

Note We recommend that you retire any signatures that you are not using. This improves sensor performance.

Button and Right-Click Menu Functions:

• Threat Profile—Lets you apply, change, or remove a threat profile.
• Edit Actions—Opens the Edit Actions dialog box.
• Enable—Enables the selected signature.
• Disable—Disables the selected signature.
• Set Severity To—Lets you set the severity level that the signature will report: High, Medium, Low or Informational.
• Restore Default—Returns all parameters to the default settings for the selected signature.
• MySDN—Takes you to the description of that signature on the MySDN site on Cisco.com.
• Edit—Opens the Edit Signature dialog box. In the Edit Signature dialog box, you can change the parameters associated with the selected signature and effectively tune the signature. You can edit only one signature at a time.
• Add—Opens the Add Signature dialog box. In the Add Signature dialog box, you can add the parameters associated with the selected signature and effectively tune the signature.
• Delete—Deletes the selected custom signature.You cannot delete built-in signatures.
• Clone—Opens the Clone Signature dialog box. In the Clone Signature dialog box, you can create a signature by changing the prepopulated values of the existing signature you chose to clone.
• Change Status To—Lets you change the status to Active, Retired, Low Memory Retired, Medium Memory Retired.
• Export—Lets you export currently displayed signatures in the table to a comma-separated Excel file (using CSV) or HTML file. You can also use Ctrl-C to copy the contents in to a clipboard and later paste in to Notepad or Word using Ctrl-V .

Add, Clone, and Edit Signatures Dialog Boxes

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following fields are found in the Add, Clone, and Edit Signature dialog boxes:

• Signature Definition—Defines the signature:

– Signature ID—Identifies the unique numerical value assigned to this signature. This value lets the sensor identify a particular signature. The value is 1000 to 65000.

– SubSignature ID—Identifies the unique numerical value assigned to this subsignature. The subsignature ID identifies a more granular version of a broad signature. The value is 0 to 255.

– Alert Severity—Lets you choose the severity level of the signature: High, Informational, Low, Medium.

– Sig Fidelity Rating—Lets you choose the weight associated with how well this signature might perform in the absence of specific knowledge of the target. The value is 0 to 100. The default is 75.

– Promiscuous Delta—Lets you determine the seriousness of the alert.

• Sig Description—Lets you specify the following attributes that help you distinguish this signature from other signatures:

– Signature Name—Specifies the name your signature. The default is MySig.

– Alert Notes—Lets you add alert notes in this field.

– User Comments—Lets you add your comments about this signature in this field.

– Alarm Traits—Lets you add the alarm trait in this field. The value is 0 to 65535. The default is 0.

– Release—Lets you add the software release in which the signature first appeared.

– Signature Creation Date—Specifies the date this signature was created.

– Signature Type—Specifies the type of signature (anomaly, component, exploit, other, vulnerability)

• Engine—Lets you choose the engine that parses and inspects the traffic specified by this signature.
• Event Action—Lets you assign the actions the sensor takes when it responds to events.
• Event Counter—Lets you configure how the sensor counts events. For example, you can specify that you want the sensor to send an alert only if the same signature fires 5 times for the same address set:

– Event Count—Specifies the number of times an event must occur before an alert is generated. The value is 1 to 65535. The default is 1.

– Event Count Key—Specifies the storage type used to count events for this signature. Choose attacker address, attacker address and victim port, attacker and victim addresses, attacker and victim addresses and ports, or victim address. The default is attacker address.

– Specify Alert Interval—Specifies the time in seconds before the event count is reset. Choose Yes or No from the drop-down list and then specify the amount of time.

• Alert Frequency — Lets you configure how often the sensor alerts you when this signature is firing. Specify the following parameters for this signature:

– Summary Mode—Specifies the mode of alert summarization. Choose Fire All, Fire Once, Global Summarize, or Summarize.

Note When multiple contexts from the adaptive security appliance are contained in one virtual sensor, the summary alerts contain the context name of the last context that was summarized. Thus, the summary is the result of all alerts of this type from all contexts that are being summarized.

– Summary Interval—Specifies the time in seconds used in each summary alert. The value is 1 to 65535. The default is 15.

– Summary Key—Specifies the storage type used to summarize alerts. Choose Attacker address, Attacker address and victim port, Attacker and victim addresses, Attacker and victim addresses and ports, or Victim address. The default is Attacker address.

– Specify Global Summary Threshold —Lets you specify the threshold number of events to take the alert into global summary. Choose Yes or No and then specify the threshold number of events .

• Status—Lets you enable or disable a signature, or retire or unretire a signature:

– Enabled—Lets you choose whether the signature is enabled or disabled.The default is yes (enabled).

– Retired—Let you choose whether the signature is retired or not and whether it is low memory retired or medium memory retired. The default is no (not retired). Low memory retired platforms have less that 1 GB of maximum sensor memory. Medium memory retired platforms have at least 1 GB and less than 2 GB of maximum sensor memory. As the signatures are loaded, the value of retired is evaluated based on the platform loading the signatures.

– Obsoletes—Specifies the list of the signatures that are obsoleted by this signature.

– Vulnerable OS List—Lets you choose a vulnerable OS for this signature.

• Mars Category—Lets you map this signature to a MARS attack category. This is a static information category that you can view in the alerts.

Edit Actions Dialog Box

An event action is the response of the sensor to an event. Event actions are configurable on a per-signature basis. The following fields are found in the Edit Actions dialog box:

• Alert and Log Actions

– Produce Alert—Writes the event to Event Store as an alert.

Note The Product Alert action is not automatic when you enable alerts for a signature. To have an alert created in the Event Store, you must select Product Alert. If you add a second action, you must include Product Alert if you want an alert sent to the Event Store. Also, every time you configure the event actions, a new list is created and it replaces the old list. Make sure you include all the event actions you need for each signature.

Note A Produce Alert event action is added for an event when global correlation has increased the risk rating of an event, and has added either the Deny Packet Inline or Deny Attacker Inline event action.

– Produce Verbose Alert—Includes an encoded dump of the offending packet in the alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.

– Log Attacker Packets—Starts IP logging on packets that contain the attacker address and sends an alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.

– Log Victim Packets—Starts IP Logging on packets that contain the victim address and sends an alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.

– Log Attacker/Victim Pair Packets—(Inline mode only) Starts IP Logging on packets that contain the attacker/victim address pair. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.

– Request SNMP Trap—Sends a request to NotificationApp to perform SNMP notification. This action causes an alert to be written to Event Store, even if Produce Alert is not selected. You must have SNMP configured on the sensor to implement this action.

• Deny Actions

– Deny Packet Inline (inline only)—Does not transmit this packet.

Note You cannot delete the event action override for Deny Packet Inline because it is protected. If you do not want to use that override, disable it.

– Deny Connection Inline (inline only)—Does not transmit this packet and future packets on the TCP flow.

– Deny Attacker Victim Pair Inline (inline only)—Does not transmit this packet and future packets on the attacker/victim address pair for a specified period of time.

Note For deny actions, to set the specified period of time and maximum number of denied attackers, choose Configuration > Policies > Event Action Rules > rules0 > General Settings.

– Deny Attacker Service Pair Inline (inline only)—Does not transmit this packet and future packets on the attacker address victim port pair for a specified period of time.

– Deny Attacker Inline (inline only)—Does not transmit this packet and future packets originating from the attacker address for a specified period of time. The sensor maintains a list of attackers being denied by the system. To remove an entry from the denied attacker list, you can view the list of attackers and clear the entire list, or you can wait for the timer to expire. The timer is a sliding timer for each entry. Therefore, if attacker A is being denied, but issues another attack, the timer for attacker A is reset and attacker A remains in the denied attacker list until the timer expires. If the denied attacker list is at capacity and cannot add a new entry, the packet is still denied.

Note This is the most severe of the deny actions. It denies current and future packets from a single attacker address. To clear all denied attacker entries, choose Configuration > Sensor Management > Time-Based Actions > Denied Attackers > Clear List, which permits the addresses back on the network.

– Modify Packet Inline (inline only)— Modifies packet data to remove ambiguity about what the end point might do with the packet.

Note You cannot use Modify Packet Inline as an action when adding event action filters or overrides.

• Other Actions

– Request Block Connection—Sends a request to ARC to block this connection. You must have blocking devices configured to implement this action.

Note Connection blocks and network blocks are not supported on adaptive security appliances. Adaptive security appliances only support host blocks with additional connection information.

Note IPv6 does not support Request Block Connection.

– Request Block Host—Sends a request to ARC to block this attacker host. You must have blocking devices configured to implement this action.

Note To set the duration of the block, choose Configuration > Policies > Event Action Rules > rules0 > General Settings.

Note IPv6 does not support Request Block Host.

– Request Rate Limit—Sends a rate limit request to ARC to perform rate limiting. You must have rate limiting devices configured to implement this action.

Note Request Rate Limit applies to a select set of signatures.

Note IPv6 does not support Request Rate Limit.

– Reset TCP Connection—Sends TCP resets to hijack and terminate the TCP flow. Reset TCP Connection only works on TCP signatures that analyze a single connection. It does not work for sweeps or floods.

Understanding Deny Packet Inline

For signatures that have Deny Packet Inline configured as an action or for an event action override that adds Deny Packet Inline as an action, the following actions may be taken:

• Dropped Packet
• Denied Flow
• TCP One Way Reset Sent TCP

The Deny Packet Inline action is represented as a dropped packet action in the alert. When a Deny Packet Inline occurs for a TCP connection, it is automatically upgraded to a Deny Connection Inline action and seen as a denied flow in the alert. If the IPS denies just one packet, the TCP continues to try to send that same packet again and again, so the IPS denies the entire connection to ensure it never succeeds with the resends.

When a Deny Connection Inline occurs, the IPS also automatically sends a TCP one-way reset, which shows up as a TCP one-way reset sent in the alert. When the IPS denies the connection, it leaves an open connection on both the client (generally the attacker) and the server (generally the victim). Too many open connections can result in resource problems on the victim. So the IPS sends a TCP reset to the victim to close the connection on the victim side (usually the server), which conserves the resources of the victim. It also prevents a failover that would otherwise allow the connection to fail over to a different network path and reach the victim. The IPS leaves the attacker side open and denies all traffic from it.

TCP Reset Differences Between IPS Appliances and ASA IPS Modules

The IPS appliance sends TCP reset packets to both the attacker and victim when Reset TCP Connection is selected. The IPS appliance sends a TCP reset packet only to the victim under the following circumstances:

• When a Deny Packet Inline or Deny Connection Inline is selected
• When TCP-based signatures and Reset TCP Connection have NOT been selected

In the case of the ASA 5500-X IPS SSP and ASA 5585-X IPS SSP, the TCP reset request is sent to the ASA, and then the ASA sends the TCP reset packets. The ASA sends TCP reset packets to both the attacker and victim when the TCP Connection is selected. When Deny Packet Inline or Deny Connection Inline is selected, the ASA sends the TCP reset packet to either the attacker or victim depending on the configuration of the signature. Signatures configured to swap the attacker and victim when reporting the alert can cause the ASA to send the TCP reset packet to the attacker.

TCP Normalizer Signature Warning

You receive the following warning if you disable a default-enabled TCP Normalizer signature or remove a default-enabled Modify Packet Inline, Deny Packet Inline, or Deny Connection Inline action:

For More Information

• For the procedure for clearing the denied attackers list and setting the duration of the block, see Configuring and Monitoring Denied Attackers.
• For the procedure for setting the specified period of time and maximum number of denied attackers, see Configuring General Settings.
• For the procedure for configuring blocking devices to implement the request block connection, request block host, and request rate limit actions, see Chapter13, “Configuring Attack Response Controller for Blocking and Rate Limiting”
• For more information on rate limiting, see Understanding Rate Limiting.
• For the procedure for configuring SNMP traps, see Configuring SNMP Traps.

Applying, Changing, and Removing Signature Threat Profiles

Note Only one threat profile per signature instance is allowed. Make sure that you have already created a signature instance before applying the threat profile.

To apply, change, and remove signature threat profiles, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To apply a threat profile, follow these steps:

a. Click Threat Profile > Apply . The following message appears:

b. Click OK .

c. In the Apply Threat Profile dialog box, from the drop-down menu, select the threat profile you want to apply to this signature, and then click OK :

– SCADA—Default signature set plus SCADA-specific signatures, that is, signatures for protecting Industrial Control Systems (ICS).

– Edge—Default signature set plus signatures that help in securing an Internet connection.

– Web_Applications—Default signature set plus signatures for protecting web server farms.

– Data_Center—Default signature set plus signatures for protecting data centers.

d. Click OK . The following message appears:

Step 4 To change a threat profile, follow these steps:

a. Click Threat Profile > Change . The following message appears:

b. Click OK .

c. In the Change Threat Profile dialog box, from the drop-down menu, select the threat profile you want to change t o for this signature, and then click OK :

– SCADA—Default signature set plus SCADA-specific signatures, that is, signatures for protecting Industrial Control Systems (ICS).

– Edge—Default signature set plus signatures that help in securing an Internet connection.

– Web_Applications—Default signature set plus signatures for protecting web server farms.

– Data_Center—Default signature set plus signatures for protecting data centers.

d. Click OK . The following message appears:

Step 5 To remove a threat profile, click Threat Profile > Remove , and click Yes to remove it.

Tip To discard your changes, click Reset.

Step 6 Click Apply to apply your changes and save the revised configuration.

Enabling, Disabling, and Retiring Signatures

To enable, disable, and retire signatures, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To locate a signature, choose a sorting option from the Filter drop-down list. For example, if you are searching for a Flood Host signature, chose Engine from the drop-down list, then Flood Host , and then select the individual signature. The sig0 pane refreshes and displays only those signatures that match your sorting criteria.

Step 4 To enable or disable an existing signature, select the signature, and follow these steps:

a. View the Enabled column to determine the status of the signature. A signature that is enabled has the check box checked.

b. To enable a signature that is disabled, check the Enabled check box.

c. To disable a signature that is enabled, remove the check from the Enabled check box.

d. To retire one or more signatures, select the signature(s), right-click, and then click Change Status To > Retired .

Note We recommend that you retire any signatures that you are not using. This improves sensor performance.

Tip To discard your changes, click Reset.

Step 5 Click Apply to apply your changes and save the revised configuration.

Adding Signatures

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

To create a custom signature that is not based on an existing signature, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures , and then click Add .

Step 3 In the Signature ID field, enter a unique signature ID for the new signature. Custom signature IDs start at 60000.

Step 4 In the Subsignature field, enter a unique subsignature ID for the new signature.

Step 5 From the Alert Severity drop-down list, choose the severity you want to associate with this signature.

Step 6 In the Sig Fidelity Rating field, enter a value between 1 and 100 to represent the signature fidelity rating for this signature.

Step 7 In the Promiscuous Delta field, enter the promiscuous delta (between 0 and 30) that you want to associate with this signature.

Step 8 Complete the Sig Description fields and add any comments about this signature.

Step 9 From the Engine drop-down list, choose the engine the sensor will use to enforce this signature.

Note If you do not know which engine to select, use the Custom Signature Wizard to help you create a custom signature.

Step 10 Assign actions to this signature.

Step 11 Configure the engine-specific parameters for this signature.

Step 12 Configure the Event Counter:

a. In the Event Count field, enter the number of events you want counted (1 to 65535).

b. From the Event Count Key drop-down list, choose the key you want to use.

c. From the Specify Alert Interface drop-down list, choose whether you want to specify the alert interval (Yes or No).

d. If you chose Yes, enter the alert interval (2 to 1000) in the Alert Interval field.

Step 13 Configure the alert frequency.

Step 14 Configure the status of the signature:

a. From the Enabled drop-down list, choose Yes to enable the signature.

Note A signature must be enabled for the sensor to actively detect the attack specified by the signature.

b. From the Retired drop-down list, choose Yes to make sure the signature is active. This places the signature in the engine.

Note A signature must not be retired for the sensor to actively detect the attack specified by the signature.

c. Choose the vulnerable OS(es).

Tip To select more than one OS, hold down the Ctrl key.

Step 15 Choose the MARS category and click OK .

Tip To discard your changes and close the Add Signature dialog box, click Cancel.

Step 16 Click OK . The new signature appears in the list with the Type set to Custom.

Tip To discard your changes, click Reset.

Step 17 Click Apply to apply your changes and save the revised configuration.

For More Information

• If you do not know which signature engine to use, use the Signature Wizard to help you create the new signature. For more information, see Chapter8, “Using the Signature Wizard”
• For the procedure for assigning actions to a signature, see Assigning Actions to Signatures.
• For the procedure for configuring alert frequency, see Configuring Alert Frequency.

Cloning Signatures

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

On the sig0 pane, you can create a signature by cloning an existing signature. This task can save you time when you are creating signatures that are similar.

To create a signature by using an existing signature as the starting point, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To locate a signature, choose a sorting option from the Filter drop-down list. For example, if you are searching for a Flood Host signature, choose Engine from the drop-down list, then Flood Host , and then select the individual signature. The sig0 pane refreshes and displays only those signatures that match your sorting criteria.

Step 4 Select the signature and click Clone .

Step 5 In the Signature field, enter a unique signature ID for the new signature. Custom signature IDs start at 60000.

Step 6 In the Subsignature field, enter a unique subsignature ID for the new signature.

Step 7 Review the parameter values and change the value of any parameter you want to be different for this new signature.

Tip To select more than one OS or event action, hold down the Ctrl key.

Step 8 Configure the status of the signature:

a. From the Enabled drop-down list, choose Yes to enable the signature.

Note A signature must be enabled for the sensor to actively detect the attack specified by the signature.

b. From the Retired drop-down list, choose Yes to make sure the signature is active. This places the signature in the engine.

Note A signature must not be retired for the sensor to actively detect the attack specified by the signature.

Tip To discard your changes and close the Clone Signature dialog box, click Cancel.

c. Click OK . The cloned signature now appears in the list with the Type set to Custom.

Tip To discard your changes, click Reset.

Step 9 Click Apply to apply your changes and save the revised configuration.

For More Information

For the procedure for configuring alert frequency, see Configuring Alert Frequency.

Tuning Signatures

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

You can tune built-in signatures by adjusting several signature parameters. Built-in signatures that have been modified are called tuned signatures. On the sig0 pane, you can edit, or tune a signature.

To tune an existing signature, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To locate a signature, choose a sorting option from the Filter drop-down list. For example, if you are searching for a Flood Host signature, choose Engine from the drop-down list, then Flood Host , and then select the individual signature. The sig0 pane refreshes and displays only those signatures that match your sorting criteria.

Step 4 Select the signature and click Edit .

Step 5 Review the parameter values and change the value of any parameter you want to tune.

Tip To select more than one OS, event action, vulnerable OS, or MARS category, hold down the Ctrl key.

Step 6 Configure the status of the signature:

a. From the Enabled drop-down list, choose Yes to enable the signature.

Note A signature must be enabled for the sensor to actively detect the attack specified by the signature.

b. From the Retired drop-down list, choose Yes to make sure the signature is active. This places the signature in the engine.

Note A signature must not be retired for the sensor to actively detect the attack specified by the signature.

Tip To discard your changes and close the Edit Signature dialog box, click Cancel.

Step 7 Click OK . The edited signature now appears in the list with the Type set to Tuned.

Tip To discard your changes, click Reset.

Step 8 Click Apply to apply your changes and save the revised configuration.

For More Information

For the procedure for configuring alert frequency, see Configuring Alert Frequency.

Assigning Actions to Signatures

On the sig0 pane, you can assign actions to a signature.

To edit actions for a signature or a set of signatures, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To locate a signature, choose a sorting option from the Filter drop-down list. For example, if you are searching for a Flood Host signature, choose Engine from the drop-down list, then Flood Host , and then select the individual signature. The sig0 pane refreshes and displays only those signatures that match your sorting criteria.

Step 4 Select the signature(s), and click Edit Actions .

Step 5 Check the check boxes next to the actions you want to assign to the signature(s).

Note A check mark indicates that the action is assigned to the selected signature(s). No check mark indicates that the action is not assigned to any of the selected signatures. A gray check mark indicates that the action is assigned to some of the selected signatures.

Tip To select more than one action, hold down the Ctrl key.

Choose from the following actions:

• Produce Alert—Writes the event to Event Store as an alert.
• Produce Verbose Alert—Includes an encoded dump of the offending packet in the alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.
• Log Attacker Packets—Starts IP logging on packets that contain the attacker address and sends an alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.
• Log Victim Packets—Starts IP Logging on packets that contain the victim address and sends an alert. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.
• Log Pair Packets—Starts IP Logging on packets that contain the attacker/victim address pair. This action causes an alert to be written to Event Store, even if Produce Alert is not selected.
• Request SNMP Trap—Sends a request to NotificationApp to perform SNMP notification. This action causes an alert to be written to Event Store, even if Produce Alert is not selected. You must have SNMP configured on the sensor to implement this action.
• Deny Packet Inline (inline only)—Does not transmit this packet.
• Deny Connection Inline (inline only)—Does not transmit this packet and future packets on the TCP flow.
• Deny Attacker Victim Pair Inline (inline only)—Does not transmit this packet and future packets on the attacker/victim address pair for a specified period of time.
• Deny Attacker Service Pair Inline (inline only)—Does not transmit this packet and future packets on the attacker address victim port pair for a specified period of time.
• Deny Attacker Inline (inline only)—Does not transmit this packet and future packets originating from the attacker address for a specified period of time.
• Modify Packet Inline (inline only)—Modifies packet data to remove ambiguity about what the end point might do with the packet.
• Request Block Connection—Sends a request to ARC to block this connection. You must have blocking devices configured to implement this action.
• Request Block Host—Sends a request to ARC to block this attacker host. You must have blocking devices configured to implement this action.
• Request Rate Limit—Sends a rate limit request to ARC to perform rate limiting. You must have rate limiting devices configured to implement this action.
• Reset TCP Connection—Sends TCP resets to hijack and terminate the TCP flow. Reset TCP Connection only works on TCP signatures that analyze a single connection. It does not work for sweeps or floods.

Tip To discard your changes and close the Assign Actions dialog box, click Cancel.

Step 6 Click OK to save your changes and close the dialog box. The new action(s) now appears in the Action column.

Tip To discard your changes, click Reset.

Step 7 Click Apply to apply your changes and save the revised configuration.

For More Information

• For the procedure for clearing the denied attackers list and setting the duration of the block, see Configuring and Monitoring Denied Attackers.
• For the procedure for setting the specified period of time and maximum number of denied attackers, see Configuring General Settings.
• For the procedure for configuring blocking devices to implement the request block connection, request block host, and request rate limit actions, see Chapter13, “Configuring Attack Response Controller for Blocking and Rate Limiting”
• For more information on rate limiting, see Understanding Rate Limiting.
• For the procedure for configuring SNMP traps, see Configuring SNMP Traps.

Configuring Alert Frequency

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

You can control how often a signature fires. For example, you may want to decrease the volume of alerts sent out from the sensor. Or you may want the sensor to provide basic aggregation of signature firings into a single alert. Or you may want to counter anti-IPS tools such as “stick,” which are designed to send bogus traffic so that the IPS produces thousands of alerts during a very short time.

To configure the alert frequency of a signature, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 Click Add to add a signature, choose a signature to clone, and click Clone , or choose a signature to edit, and click Edit .

Step 4 Configure the event count, key, and alert interval:

a. In the Event Count field, enter a value for the event count. This is the minimum number of hits the sensor must receive before sending one alert for this signature.

b. From the Event Count Key drop-down list, choose an attribute to use as the Event Count Key. For example, if you want the sensor to count events based on whether or not they are from the same attacker, choose Attacker address as the Event Count Key.

c. If you want to count events based on a rate, choose Yes from the Specify Event Interval drop-down list, and then in the Alert Interval field, enter the number of seconds that you want to use for your interval.

Step 5 To control the volume of alerts and configure how the sensor summarizes alerts, choose one of the following options from the Summary Mode drop-down list:

• Fire All— Specifies that you want the sensor to send an alert every time the signature detects malicious traffic. You can then specify additional thresholds that let the sensor dynamically adjust the volume of alerts. Go to Step 6.
• Fire Once—Specifies that you want the sensor to send an alert the first time the signature detects malicious traffic. You can then specify additional thresholds that let the sensor dynamically adjust the volume of alerts. Go to Step 7.
• Summarize—Specifies that you want the sensor to only send summary alerts for this signature instead of sending alerts every time the signature fires. You can then specify additional thresholds that let the sensor dynamically adjust the volume of alerts. Go to Step 8.
• Global Summarize—Specifies that you want the sensor to send an alert the first time a signature fires on an address set, and then only send a global summary alert that includes a summary of all alerts for all address sets over a given time interval. Go to Step 9.

Step 6 Configure the Fire All option:

a. From the Specify Summary Threshold drop-down list, choose Yes .

b. In the Summary Threshold field, enter the minimum number of hits the sensor must receive before sending a summary alert for this signature.

c. In the Summary Interval field, enter the number of seconds that you want to use for the time interval.

d. To have the sensor enter global summarization mode, choose Yes from the Specify Global Summary Threshold drop-down list.

e. In the Global Summary Threshold field, enter the minimum number of hits the sensor must receive before sending a global summary alert.

f. From the Summary Key drop-down list, choose the type of summary key. The summary key identifies the attribute to use for counting events. For example, if you want the sensor to count events based on whether or not they are from the same attacker, choose Attacker address as the summary key.

Step 7 Configure the Fire Once option:

a. From the Summary Key drop-down list, choose the type of summary key. The summary key identifies the attribute to use for counting events. For example, if you want the sensor to count events based on whether or not they are from the same attacker, choose Attacker address as the summary key.

b. To have the sensor use global summarization, choose Yes from the Specify Global Summary Threshold drop-down list.

c. In the Global Summary Threshold field, enter the minimum number of hits the sensor must receive before sending a global summary alert. When the alert rate exceeds a specified number of signatures in a specified number of seconds, the sensor changes from sending a single alert the first time a signature fires to sending a single global summary alert. When the rate during the interval drops below this threshold, the sensor reverts to its configured alert behavior.

Note When multiple contexts from the adaptive security appliance are contained in one virtual sensor, the summary alerts contain the context name of the last context that was summarized. Thus, the summary is the result of all alerts of this type from all contexts that are being summarized.

d. In the Summary Interval field, enter the number of seconds during which the sensor counts events for summarization.

Step 8 Configure the Summarize option:

a. In the Summary Interval field, enter the number of seconds during which the sensor counts events for summarization.

b. From the Summary Key drop-down list, choose the type of summary key. The summary key identifies the attribute to use for counting events. For example, if you want the sensor to count events based on whether or not they are from the same attacker, choose Attacker address as the summary key.

c. To have the sensor use dynamic global summarization, choose Yes from the Specify Global Summary Threshold drop-down list.

d. In the Global Summary Threshold field, enter the minimum number of hits the sensor must receive before sending a global summary alert.

Note When the alert rate exceeds a specified number of signatures in a specified number of seconds, the sensor changes from sending a single alert the first time a signature fires to sending a single global summary alert. When the rate during the interval drops below this threshold, the sensor reverts to its configured alert behavior.

Step 9 To configure the Global Summarize option, in the Summary Interval field, enter the number of seconds during which the sensor counts events for summarization.

Step 10 Click OK to save your alert behavior changes. You are returned to the sig0 pane.

Tip To discard your changes, click Cancel.

Step 11 To apply your alert behavior changes to the signature configuration, click Apply . The signature you added or edited is enabled and added to the list of signatures.

Example Meta Engine Signature

The Meta engine defines events that occur in a related manner within a sliding time interval. This engine processes events rather than packets. As signature events are generated, the Meta engine inspects them to determine if they match any or several Meta definitions. The Meta engine generates a signature event after all requirements for the event are met.

All signature events are handed off to the Meta engine by the Signature Event Action Processor. The Signature Event Action Processor hands off the event after processing the minimum hits option. Summarization and event action are processed after the Meta engine has processed the component events.

Note The Meta engine is different from other engines in that it takes alerts as input where most engines take packets as input.

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following example demonstrates how to create a signature based on the Meta engine. For example, the following custom signature fires when it sees the alerts from signature 2000 subsignature 0 and signature 3000 subsignature 0 on the same source address. The source address selection is a result of the meta key default value of Axxx. You can change the behavior by changing the meta key setting to xxBx (destination address) for example.

To create a signature based on the Meta engine, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures , and then click Add .

Step 3 In the Signature ID field, enter a unique signature ID for the new signature. Custom signature IDs start at 60000.

Step 4 In the Subsignature field, enter a unique subsignature ID for the new signature.

Step 5 From the Alert Severity drop-down list, choose the severity you want to associate with this signature.

Step 6 In the Signature Fidelity Rating field, enter a value between 1and 100 to represent the signature fidelity rating for this signature.

Step 7 Leave the default value for the Promiscuous Delta field.

Step 8 Complete the signature description fields and add any comments about this signature.

Step 9 From the Engine drop-down list, choose Meta .

Step 10 Configure the Meta engine-specific parameters:

a. From the Event Action drop-down list, choose the actions you want the sensor to take when it responds to an event.

Tip To choose more than one action, hold down the Ctrl key.

b. From the Swap Attacker Victim drop-down list, choose Yes to swap the destination and source ports in the alert message.

c. In the Meta Reset Interval field, enter the time in seconds to reset the Meta signature. The valid range is 0 to 3600 seconds. The default is 60 seconds.

d. Click the pencil icon next to Component List to insert the new Meta signature. The Component List dialog box appears.

e. Click Add to insert the first Meta signature. The Add List Entry dialog box appears.

f. In the Entry Key field, enter a name for the entry, for example, Entry1. The default is MyEntry.

g. In the Component Sig ID field, enter the signature ID of the signature (2000 in this example) on which to match this component.

h. In the Component SubSig ID field, specify the subsignature ID of the signature (0 in this example) on which to match this component.

i. In the Component Count field, enter the number of times this component must fire before it is satisfied.

j. In the Is a NOT component field, choose Yes if you want this to be NOT component.

k. Click OK . You are returned to the Add List Entry dialog box.

l. Select your entry and click Select to move it to the Selected Entries list.

m. Click OK .

n. Click Add to insert the next Meta signature. The Add List Entry dialog box appears.

o. In the Entry Key field, enter a name for the entry, for example Entry2.

p. In the Component Sig ID field, enter the signature ID of the signature (3000 in this example) on which to match this component.

q. In the Component SubSig ID field, enter the subsignature ID of the signature (0 in this example) on which to match this component.

r. In the Component Count field, enter the number of times this component must fire before it is satisfied.

s. Click OK . You are returned to the Add List Entry dialog box.

t. Select your entry and click Select to move it to the Selected Entries list.

u. Select the new entry and click Move Up or Move Down to order the new entry.

Tip Click Reset Ordering to return the entries to the Entry Key list.

v. Click OK .

w. From the Meta Key drop-down list, choose the storage type for the Meta signature:

• Attacker address
• Attacker and victim addresses
• Attacker and victim addresses and ports
• Victim address

x. In the Unique Victims field, enter the number of unique victims required for this signature. The valid value is 1 to 256. The default is 1.

y. From the Component List in Order drop-down list, choose Yes to have the component list fire in order.

Step 11 In the Component List in Order field, you can choose Yes to have the component list fire in order. For example, if signature 3000 in the Entry2 component fires before signature 2000 in the Entry1 component, the custom Meta signature will not fire.

Step 12 In the All Components Required field and the All NOT Components Required field, choose Yes to use all components and NOT components. This option works with the All NOT Components Required option, if you have NOT components configured as required, the Meta signature will not fire.

Step 13 Configure Event Counter:

a. In the Event Count field, enter the number of events you want counted (1 to 65535).

b. From the Event Count Key drop-down list, choose the key you want to use.

c. From the Specify Alert Interface drop-down list, choose whether you want to specify the alert interval (Yes or No).

d. If you chose Yes, enter the alert interval (2 to 1000) in the Alert Interval field.

Step 14 Configure the alert frequency.

Step 15 Leave the default ( Yes) for the Enabled field.

Note A signature must be enabled for the sensor to actively detect the attack specified by the signature.

Step 16 Leave the default ( Yes) for the Retired field. This places the signature in the engine.

Note A signature must not be retired for the sensor to actively detect the attack specified by the signature.

Step 17 From the Vulnerable OS List drop-down list, choose the operating systems that are vulnerable to this signature.

Tip To choose more than one action, hold down the Ctrl key.

Step 18 From the Mars Category drop-down list, choose the MARS categories you want this signature to identify.

Tip To choose more than one action, hold down the Ctrl key.

Tip To discard your changes and close the Add Signature dialog box, click Cancel.

Step 19 Click OK . The new signature appears in the list with the Type set to Custom.

Tip To discard your changes, click Reset.

Step 20 Click Apply to apply your changes and save the revised configuration.

Example Atomic IP Advanced Engine Signature

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following example demonstrates how to create a signature based on the Atomic IP Advanced engine. For example, the following custom signature matches any packets that are IPv6 with a HOP Option Header where the header is type 1 and the length is 8.

To create a signature based on the Atomic IP Advanced engine, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures , and then click Add .

Step 3 In the Signature ID field, enter a unique signature ID for the new signature. Custom signature IDs start at 60000.

Step 4 In the Subsignature field, enter a unique subsignature ID for the new signature.

Step 5 From the Alert Severity drop-down list, choose the severity you want to associate with this signature.

Step 6 In the Signature Fidelity Rating field, enter a value between 1and 100 to represent the signature fidelity rating for this signature.

Step 7 Leave the default value for the Promiscuous Delta field.

Step 8 Complete the signature description fields and add any comments about this signature.

Step 9 From the Engine drop-down list, choose Atomic IP Advanced .

Step 10 Configure the Atomic IP Advanced engine-specific parameters:

a. From the Event Action drop-down list, choose the actions you want the sensor to take when it responds to an event.

Note IPv6 does not support the following event actions: Request Block Host, Request Block Connection, or Request Rate Limit.

Tip To choose more than one action, hold down the Ctrl key.

b. From the IP Version drop-down list, choose Yes to enable the IP version, and then from the IP Version drop-down list, choose IPv6 to enable IPv6.

c. From the HOP Options Header drop-down list, choose Yes to enable hop-by-hop options, and then from the HOH Present drop-down list, choose Have HOH .

d. From the HOH Options field, choose Yes , and then in the HOH Option Type field, enter 1 .

e. In the HOH Option Length drop-down list, choose Yes to enable hop-by-hop length, and then in the HOH Option Length field, enter 8 .

Step 11 Configure Event Counter:

a. In the Event Count field, enter the number of events you want counted (1 to 65535).

b. From the Event Count Key drop-down list, choose the key you want to use.

c. From the Specify Alert Interface drop-down list, choose whether you want to specify the alert interval (Yes or No).

d. If you chose Yes, enter the alert interval (2 to 1000) in the Alert Interval field.

Step 12 Configure the alert frequency.

Step 13 Leave the default ( Yes) for the Enabled field.

Note A signature must be enabled for the sensor to actively detect the attack specified by the signature.

Step 14 Leave the default ( Yes) for the Retired field. This places the signature in the engine.

Note A signature must not be retired for the sensor to actively detect the attack specified by the signature.

Step 15 From the Vulnerable OS List drop-down list, choose the operating systems that are vulnerable to this signature.

Tip To choose more than one action, hold down the Ctrl key.

Step 16 From the Mars Category drop-down list, choose the MARS categories you want this signature to identify.

Tip To choose more than one action, hold down the Ctrl key.

Tip To discard your changes and close the Add Signature dialog box, click Cancel.

Step 17 Click OK . The new signature appears in the list with the Type set to Custom.

Tip To discard your changes, click Reset.

Step 18 Click Apply to apply your changes and save the revised configuration.

Example String XL TCP Engine Match Offset Signature

Note This procedure also applies to String XLUDP and String XL ICMP signatures, with the exception of the parameter service-ports, which does not apply to String XL ICMP signatures.

You can create a custom String XL TCP signature by either cloning an existing String XL TCP signature and then tuning it, or by adding a new signature and assigning the String XL TCP signature engine to it.

The following example demonstrates how to create a custom String XL TCP signature that searches for exact, maximum, or minimum offsets. You can modify the following optional match offset parameters for this custom String XLTCP signature:

• Specify Exact Match Offset {Yes | No}—Enables exact match offset:

– Exact Match Offset—Specifies the exact stream offset in bytes the regular expression string must report for a match to be valid. The valid value is 0 to 65535.

• Specify Maximum Match Offset {Yes | No}—Enables maximum match offset:

– Maximum Match Offset—Specifies the maximum stream offset in bytes the regular expression string must report for a match to be valid. The valid value is 0 to 65535.

• Specify Min Match Offset {Yes | No}—Enables minimum match offset:

– Min Match Offset—Specifies the minimum stream offset in bytes the regular expression string must report for a match to be valid. The valid value is 0 to 65535.

To create a custom String XL TCP signature that searches for matches, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To create a custom signature by cloning an existing String XL TCP signature, from the Filter drop-down list, choose Engine, and then String TCP XL from the signature engine drop-down list, highlight the signature you want to clone, and then click Clone . Continue with Step 5.

Step 4 To create a custom signature based on the String XL TCP engine, click Add and in the Engine field in the Add Signature dialog box, click Click to edit and choose String XL TCP from the drop-down list. Continue with Step 5.

Step 5 In the Signature ID field, enter a number for the signature. Custom signatures range from 60000 to 65000.

Step 6 In the Subsignature ID field, enter a number for the signature. The default is 0. You can assign a subsignature ID if you are grouping signatures together that are similar.

Step 7 (Optional) In the Severity Alert field, choose the severity to be reported by Event Viewer when the sensor sends an alert. The default is Medium.

Step 8 (Optional) In the Sig Fidelity Rating field, enter a value. The signature fidelity rating is a valid value between 0 and 100 that indicates your confidence in the signature, with 100 being the most confident. The default is 75.

Step 9 In the Promiscuous Delta field, enter a value. The promiscuous delta is a value used to determine the seriousness of the alert. The valid range is 0 to 30. The default is 0.

Step 10 Under Sig Description specify the attributes that uniquely identify this signature:

a. (Optional) In the Signature Name field, enter a name for the signature. A default name, My Sig, appears in the Signature Name field. Change it to a name that is more specific for your custom signature.

Note The signature name, along with the signature ID and subsignature ID, is reported to Event Viewer when an alert is generated.

b. (Optional) In the Alert Notes field, enter text to be added to the alert. You can add text to be included in alerts associated with this signature. These notes are reported to Event Viewer when an alert is generated. The default is My Sig Info.

c. (Optional) In the User Comments field, enter text that describes this signature. You can add any text that you find useful here. This field does not affect the signature or alert in any way. The default is Sig Comment.

Step 11 Under Engine, assign the engine-specific parameters:

a. (Optional) In the Event Action field, assign the event actions you want the signature to report. The default is Produce Alert. You can assign more actions, such as deny or block, based on your security policy.

Tip To select more than one action, hold down the Ctrl key.

b. (Optional) In the Strip Telnet Options field, choose Yes from the drop-down list to strip the Telnet option characters from the data before the pattern is searched.

c. From the Direction drop-down list, choose the direction of the traffic:

• From Service—Traffic from service port destined to client port.
• To Service—Traffic from client port destined to service port.

d. In the Service Ports field, enter the port number, for example, 80. The value is a comma-separated list of ports or port ranges where the target service resides.

Step 12 To specify the regular expression, in the Specify Raw Regex String, choose No from the drop-down list.

Note Raw Regex is regular expression syntax used for raw mode processing. It is expert mode only and targeted for use by the Cisco IPS signature development team or only those who are under supervision by the Cisco IPS signature development team. You can configure a String XL signature in either regular Regex or raw Regex.

a. In the Regex String field, enter the string this signature will be looking for in the TCP packet, for example, tcpstring.

b. (Optional) In the Specify Minimum Match Length field, choose Yes from the drop-down list to enable minimum match length, and then in the Minimum Match Length field, enter the minimum number of bytes the regular expression string must match (0 to 65535).

c. (Optional) In the Swap Attacker Victim field, choose Yes from the drop-down list to swap the attacker and victim addresses and ports (source and destination) in the alert message and for any actions taken.

Step 13 (Optional) In the Specify Exact Match Offset field, choose Yes from the drop-down list to enable exact match offset, and then in the Exact Match Offset field, enter the exact offset the regular expression must trigger to be considered a match for this signature (0 to 65535).

Note If you have exact match offset set to Yes, you cannot configure maximum or minimum match offset. If you have exact match offset set to No, you can configure both maximum and minimum match offset at the same time.

Step 14 (Optional) In the Specify Max Match Offset field, choose Yes from the drop-down list to enable maximum match offset, and then in the Specify Max Match Offset field, enter the maximum offset at which the regular expression must trigger to be considered a match for this signature (0 to 65535).

Step 15 (Optional) In the Specify Min Match Offset field, choose Yes from the drop-down list to enable minimum match offset, and then in the Specify Min Match Offset field, enter the minimum offset at which the regular expression must trigger to be considered a match for this signature (0 to 65535).

Step 16 (Optional) Under Alert Frequency, you can change the default alert frequency.

Step 17 Click OK to create your custom signature. The signature you created is enabled and added to the list of signatures.

Tip To discard your changes, click Cancel.

For More Information

For detailed information about the String XL signature engine, see String XL Engines.

Example String XL TCP Engine Minimum Match Length Signature

Note This procedure also applies to String XLUDP and String XL ICMP signatures, with the exception of the parameter service-ports, which does not apply to String XL ICMP signatures.

You can create a custom String XL TCP signature by either cloning an existing String XL TCP signature and then tuning it, or by adding a new signature and assigning the String XL TCP signature engine to it.

You can configure the following options to work with a specific Regex string:

• Dot All {Yes | No}—If set to Yes, matches [\x00-\xFF] including \n; if set to No, matches anything in the range [\x00-\xFF] except \n. No is the default.
• End Optional {Yes | No}—Specifies that at the end of a packet, if all other conditions are satisfied but the end is not seen, a match is reported if the minimum is exceeded
• No Case {Yes | No}—Specifies to treat all alphabetic characters in the expression as case insensitive.
• Stingy {Yes | No}—Specifies to stop looking for larger matches after the first completed match.

Note Stingy can only be used with Min Match Length; otherwise, it is ignored

• UTF-8 {True | False}—Treats all legal UTF-8 byte sequences in the expression as a single character.

The following example demonstrates how to create a custom String XL TCP signature that searches for minimum match length with stingy, dot all, and UTF-8 turned on.

To create a custom signature based on the String XL TCP engine that searches for minimum match length with stingy, dot all, and UTF-8 turned on, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 To create a custom signature by cloning an existing String XL TCP signature, from the Filter drop-down list, choose Engine, and then String TCP XL from the signature engine drop-down list, then highlight the signature you want to clone, and click Clone . Continue with Step 5.

Step 4 To create a custom signature based on the String XL TCP engine, click Add and in the Engine field in the Add Signature dialog box, click Click to edit and choose String XL TCP from the drop-down list. Continue with Step 5.

Step 5 In the Signature ID field, enter a number for the signature. Custom signatures range from 60000 to 65000.

Step 6 In the Subsignature ID field, enter a number for the signature. The default is 0. You can assign a subsignature ID if you are grouping signatures together that are similar.

Step 7 (Optional) In the Severity Alert field, choose the severity to be reported by Event Viewer when the sensor sends an alert. The default is Medium.

Step 8 (Optional) In the Sig Fidelity Rating field, enter a value. The signature fidelity rating is a valid value between 0 and 100 that indicates your confidence in the signature, with 100 being the most confident. The default is 75.

Step 9 In the Promiscuous Delta field, enter a value. The promiscuous delta is a value used to determine the seriousness of the alert. The valid range is 0 to 30. The default is 0.

Step 10 Under Sig Description specify the attributes that uniquely identify this signature:

a. (Optional) In the Signature Name field, enter a name for the signature. A default name, My Sig, appears in the Signature Name field. Change it to a name that is more specific for your custom signature.

Note The signature name, along with the signature ID and subsignature ID, is reported to Event Viewer when an alert is generated.

b. (Optional) In the Alert Notes field, enter text to be added to the alert. You can add text to be included in alerts associated with this signature. These notes are reported to Event Viewer when an alert is generated. The default is My Sig Info.

c. (Optional) In the User Comments field, enter text that describes this signature. You can add any text that you find useful here. This field does not affect the signature or alert in any way. The default is Sig Comment.

Step 11 Under Engine, assign the engine-specific parameters:

a. (Optional) In the Event Action field, assign the event actions you want the signature to report. The default is Produce Alert. You can assign more actions, such as deny or block, based on your security policy.

Tip To select more than one action, hold down the Ctrl key.

b. (Optional) In the Strip Telnet Options field, choose Yes from the drop-down list to strip the Telnet option characters from the data before the pattern is searched.

c. From the Direction drop-down list, choose the direction of the traffic:

• From Service—Traffic from service port destined to client port.
• To Service—Traffic from client port destined to service port.

d. In the Service Ports field, enter the port number, for example, 23. The value is a comma-separated list of ports or port ranges where the target service resides.

Step 12 To specify the regular expression, in the Specify Raw Regex String, choose No from the drop-down list.

Note Raw Regex is regular expression syntax used for raw mode processing. It is expert mode only and targeted for use by the Cisco IPS signature development team or only those who are under supervision by the Cisco IPS signature development team. You can configure a String XL signature in either regular Regex or raw Regex.

a. In the Regex String field, enter the string this signature will be looking for in the TCP packet (for example, ht+p[\r].).

b. (Optional) In the Specify Minimum Match Length field, choose Yes from the drop-down list to enable minimum match length, and then in the Minimum Match Length field, enter the minimum number of bytes the regular expression string must match (0 to 65535).

c. (Optional) In the Swap Attacker Victim field, choose Yes from the drop-down list to swap the attacker and victim addresses and ports (source and destination) in the alert message and for any actions taken.

Step 13 (Optional) Turn on the following options by choosing Yes in the drop-down list:

• Dot All
• Stingy
• UTF-8

Step 14 (Optional) Under Alert Frequency, you can change the default alert frequency.

Step 15 Click OK to create your custom signature. The signature you created is enabled and added to the list of signatures.

Tip To discard your changes, click Cancel.

For More Information

For detailed information about the String XL signature engine, seeString XL Engines.

Signature Variables Tab

Note You must be administrator or operator to configure signature variables.

When you want to use the same value within multiple signatures, use a variable. When you change the value of a variable, that variable is updated in all signatures in which it appears. This saves you from having to change the variable repeatedly as you configure signatures.

Note You must preface the variable with a dollar ($) sign to indicate that you are using a variable rather than a string.

Some variables cannot be deleted because they are necessary to the signature system. If a variable is protected, you cannot select it to edit it. You receive an error message if you try to delete protected variables. You can edit only one variable at a time.

Signature Variables Tab Field Definitions

The following fields are found on the Signature Variables tab and in the Add and Edit Signature Variable dialog boxes:

• Name—Identifies the name assigned to this variable.
• Type—Identifies the variable as a web port or IP address range.
• Value—Identifies the value(s) represented by this variable.

Note To designate multiple port numbers for a single variable, place a comma between the entries. For example, 80, 3128, 8000, 8010, 8080, 8888, 24326.

Adding, Editing, and Deleting Signature Variables

To add, edit, and delete signature variables, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures > Advanced > Signature Variables , and then click Add to create a variable.

Step 3 In the Name field, enter the name of the signature variable. From the Type drop-down list, choose the type of signature variable.

Note A valid name can only contain numbers or letters. You can also use a hyphen (-) or underscore (_).

Step 4 In the Value field, enter the value for the new signature variable. The web-ports type has a predefined set of ports where web servers are running, but you can edit the value. This variable affects all signatures that have web ports. The default is 80, 3128, 8000, 8010, 8080, 8888, 24326.

Note You can use commas as delimiters. Make sure there are no trailing spaces after the comma. Otherwise, you receive a Validation failed error.

Tip To discard your changes and close the Add Signature Variable dialog box, click Cancel.

Step 5 Click OK . The new variable appears in the signature variables list on the Signature Variables tab.

Step 6 To edit an existing variable, select it in the signature variables list, and then click Edit .

Step 7 Make any changes needed in the Value field.

Tip To discard your changes and close the Edit Signature Variable dialog box, click Cancel.

Step 8 Click OK . The edited variable appears in the signature variables list on the Signature Variables tab.

Step 9 To delete a variable, select it in the signature variables list, and then click Delete . The variable no longer appears in the signature variables list on the Signature Variables tab.

Tip To discard your changes, click Reset.

Step 10 Click Apply to apply your changes and save the revised configuration.

Miscellaneous Tab

Note You must be administrator or operator to configure the parameters on the Miscellaneous tab.

On the Miscellaneous tab, you can perform the following tasks:

• Configure the application policy parameters (also known as AIC signatures)

You can configure the sensor to provide Layer 4 to Layer 7 packet inspection to prevent malicious attacks related to web services. You first set up the AIC parameters, then you can either use the default AIC signatures or tune them.

• Configure IP fragment reassembly options

You can configure the sensor to reassemble a datagram that has been fragmented over multiple packets. You can specify boundaries that the sensor uses to determine how many datagrams and how long to wait for more fragments of a datagram. The goal is to ensure that the sensor does not allocate all its resources to datagrams that cannot be completely reassembled, either because the sensor missed some frame transmissions or because an attack has been launched that is based on generating random fragment datagrams. You first choose the method the sensor will use to perform IP fragment reassembly, then you can tune the IP fragment reassembly signatures, which are part of the Normalizer engine.

• Configure TCP stream reassembly

You can configure the sensor to monitor only TCP sessions that have been established by a complete three-way handshake. You can also configure how long to wait for the handshake to complete, and how long to keep monitoring a connection where no more packets have been seen. The goal is to prevent the sensor from creating alerts where a valid TCP session has not been established. There are known attacks against sensors that try to get the sensor to generate alerts by simply replaying pieces of an attack. The TCP session reassembly feature helps to mitigate these types of attacks against the sensor. You first choose the method the sensor will use to perform TCP stream reassembly, then you can tune TCP stream reassembly signatures, which are part of the Normalizer engine.

Note For signature 3050 Half Open SYN Attack, if you choose Modify Packet Inline as the action, you can see as much as 20 to 30% performance degradation while the protection is active. The protection is only active during an actual SYN flood.

• Configure IP logging options

You can configure a sensor to generate an IP session log when the sensor detects an attack. When IP logging is configured as a response action for a signature and the signature is triggered, all packets to and from the source address of the alert are logged for a specified period of time.

For More Information

• For the procedure for setting up the AIC parameters, see Configuring Application Policy.
• For an example procedure for tuning AIC signatures, see Tuning an AIC Signature.
• For the procedure for configuring the method the sensor uses for performing IP fragment reassembly, see Configuring the IP Fragment Reassembly Mode.
• For an example procedure for tuning an IP fragment reassembly signature, see Tuning an IP Fragment Reassembly Signature.
• For the procedure for configuring the method the sensor uses to perform TCP stream reassembly, see Configuring the TCP Stream Reassembly Mode.
• For an example procedure for tuning a TCP stream reassembly signature, see Tuning a TCP Stream Reassembly Signature.
• For the procedure for configuring IP logging, see Configuring IP Logging.

Miscellaneous Tab Field Definitions

The following fields are found on the Miscellaneous tab:

• Application Policy—Lets you configure application policy enforcement:

– Enable HTTP —Enables protection for web services. Check the Yes check box to require the sensor to inspect HTTP traffic for compliance with the RFC.

– Max HTTP Requests—Specifies the maximum number of outstanding HTTP requests per connection.

– AIC Web Ports—Specifies the variable for ports to look for AIC traffic.

– Enable FTP—Enables protection for web services. Check the Yes check box to require the sensor to inspect FTP traffic.

• Fragment Reassembly—Lets you configure the mode for IP fragment reassembly:

– IP Reassembly Mode—Identifies the method the sensor uses to reassemble the fragments, based on the operating system.

• Stream Reassembly—Lets you configure the mode for TCP stream reassembly:

– TCP Handshake Required—Specifies that the sensor should only track sessions for which the three-way handshake is completed.

– TCP Reassembly Mode—Specifies the mode the sensor should use to reassemble TCP sessions with the following options:

– Asymmetric—Can only see one direction of bidirectional traffic flow.

Note Asymmetric mode lets the sensor synchronize state with the flow and maintain inspection for those engines that do not require both directions. Asymmetric mode lowers security because full protection requires both sides of traffic to be seen.

– Strict—If a packet is missed for any reason, all packets after the missed packet are not processed.

– Loose—Use in environments where packets might be dropped.

• IP Log—Lets you configure the sensor to stop an in-progress IP Log when any one of the following thresholds is reached:

– Max IP Log Packets—Identifies the maximum number of packets per log. Valid values are 0 to 65535 packets. The default is 0 packets.

– IP Log Time—Identifies the duration in seconds to log. Valid values are 30 to 300 seconds. The default is 30 seconds.

– Max IP Log Bytes—Identifies the maximum size in bytes per log. Valid values are 0 to 2147483647 bytes. The default is 0 bytes.

Configuring Application Policy Signatures

This section describes Application Policy (AIC) signatures and how to configure them. This section contains the following topics:

• Understanding AIC Signatures
• AIC Engine and Sensor Performance
• AIC Request Method Signatures
• AIC MIME Define Content Type Signatures
• AIC Transfer Encoding Signatures
• AIC FTP Commands Signatures
• Configuring Application Policy
• Tuning an AIC Signature

Understanding AIC Signatures

AIC has the following categories of signatures:

• HTTP request method

– Define request method

– Recognized request methods

• MIME type

– Define content type

– Recognized content type

• Define web traffic policy

There is one predefined signature, 12674, that specifies the action to take when noncompliant HTTP traffic is seen. The parameter Alarm on Non HTTP Traffic enables the signature. By default this signature is enabled.

• Transfer encodings

– Associate an action with each method

– List methods recognized by the sensor

– Specify which actions need to be taken when a chunked encoding error is seen

• FTP commands

– Associates an action with an FTP command.

For More Information

• For more information on the AIC engine, see AIC Engine.
• For a list of AIC request method signature IDs and descriptions, see AIC Request Method Signatures.
• For a list of AIC MIME define content type signature IDs and descriptions, see AIC MIME Define Content Type Signatures.
• For a list of AIC transfer encoding signature IDs and descriptions, see AIC Transfer Encoding Signatures.
• For a list of AIC FTP commands signature IDs and descriptions, see AIC FTP Commands Signatures.

AIC Engine and Sensor Performance

Application policy enforcement is a unique sensor feature. Rather than being based on traditional IPS technologies that inspect for exploits, vulnerabilities, and anomalies, AIC policy enforcement is designed to enforce HTTP and FTP service policies. The inspection work required for this policy enforcement is extreme compared with traditional IPS inspection work. A large performance penalty is associated with using this feature. When AIC is enabled, the overall bandwidth capacity of the sensor is reduced.

AIC policy enforcement is disabled in the IPS default configuration. If you want to activate AIC policy enforcement, we highly recommend that you carefully choose the exact policies of interest and disable those you do not need. Also, if your sensor is near its maximum inspection load capacity, we recommend that you not use this feature since it can oversubscribe the sensor. We recommend that you use the adaptive security appliance firewall to handle this type of policy enforcement.

For More Information

For more information on the AIC engine, see AIC Engine.

AIC Request Method Signatures

The HTTP request method has two categories of signatures:

• Define request method—Allows actions to be associated with request methods. You can expand and modify the signatures (Define Request Method).
• Recognized request methods—Lists methods that are recognized by the sensor (Recognized Request Methods).

Table 7-1 lists the predefined define request method signatures. Enable the signatures that have the predefined method you need.

For More Information

For the procedure for enabling signatures, see Enabling, Disabling, and Retiring Signatures.

AIC MIME Define Content Type Signatures

There are two policies associated with MIME types:

• Define content type—Associates specific actions for the following cases (Define Content Type):

– Deny a specific MIME type, such as an image/jpeg

– Message size violation

– MIME-type mentioned in header and body do not match

• Recognized content type (Recognized Content Type)

Table 7-2 lists the predefined define content type signatures. Enable the signatures that have the predefined content type you need. You can also create custom define content type signatures.

For More Information

For the procedure for enabling signatures, see Enabling, Disabling, and Retiring Signatures.

AIC Transfer Encoding Signatures

There are three policies associated with transfer encoding:

• Associate an action with each method (Define Transfer Encoding)
• List methods recognized by the sensor (Recognized Transfer Encodings)
• Specify which actions need to be taken when a chunked encoding error is seen (Chunked Transfer Encoding Error)

Table 7-3 lists the predefined transfer encoding signatures. Enable the signatures that have the predefined transfer encoding method you need.

For More Information

For the procedure for enabling signatures, see Enabling, Disabling, and Retiring Signatures.

AIC FTP Commands Signatures

Table 7-4 lists the predefined FTP commands signatures. Enable the signatures that have the predefined FTP command you need.

For More Information

For the procedure for enabling signatures, see Enabling, Disabling, and Retiring Signatures.

Configuring Application Policy

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

To configure the application policy parameters, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures > Advanced > Miscellaneous .

Step 3 In the Enable HTTP field, choose Yes from the drop-down list to enable inspection of HTTP traffic.

Step 4 In the Max HTTP Requests field, enter the number of outstanding HTTP requests per connection that can be outstanding without having received a response from the server.

Step 5 In the AIC Web Ports field, enter the ports that you want to be active.

Step 6 In the Enable FTP field choose Yes from the drop-down list to enable inspection of FTP traffic.

Note If you enable the application policy for HTTP or FTP, the sensor checks to be sure the traffic is compliant with the RFC.

Tip To discard your changes, click Cancel.

Step 7 Click OK .

Tip To discard your changes, click Reset.

Step 8 Click Apply to apply your changes and save the revised configuration.

Tuning an AIC Signature

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following example demonstrates how to tune an AIC signature, a Recognized Content Type (MIME) signature, specifically, signature 12,623 1 Content Type image/tiff Invalid Message Length.

To tune a MIME-type policy signature, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures .

Step 3 From the Filter drop-down list, choose Engine and then choose AIC HTTP as the engine.

Step 4 Scroll down the list and select Sig ID 12,623 Subsig ID 1 Content Type image/tiff Invalid Message Length, and click Edit .

Tip You can click the Sig ID column head to have the signature IDs appear in order.

Step 5 Under Status, choose Yes from the drop-down list in the Enabled field.

Step 6 Under Engine, choose one of the options, for example, Length , in the Content Type Details field.

Step 7 In the Length field, make the length smaller by changing the default to 30,000.

Tip To discard your changes and close the Edit Signature dialog box, click Cancel.

Step 8 Click OK , and then click Apply to save your changes.

Tip To discard your changes, click Reset.

Configuring IP Fragment Reassembly Signatures

This section describes IP fragment reassembly, lists the IP fragment reassembly signatures with their configurable parameters, and describes how to configure them. It contains the following topics:

• Understanding IP Fragment Reassembly Signatures
• IP Fragment Reassembly Signatures and Configurable Parameters
• Configuring the IP Fragment Reassembly Mode
• Tuning an IP Fragment Reassembly Signature

Understanding IP Fragment Reassembly Signatures

You can configure the sensor to reassemble a datagram that has been fragmented over multiple packets. You can specify boundaries that the sensor uses to determine how many datagram fragments it reassembles and how long to wait for more fragments of a datagram. The goal is to ensure that the sensor does not allocate all its resources to datagrams that cannot be completely reassembled, either because the sensor missed some frame transmissions or because an attack has been launched that is based on generating random fragmented datagrams.

Note You configure the IP fragment reassembly per signature.

For More Information

For more information on the Normalizer signature engine, see Normalizer Engine.

IP Fragment Reassembly Signatures and Configurable Parameters

Table 7-5 lists IP fragment reassembly signatures with the parameters that you can configure for IP fragment reassembly. The IP fragment reassembly signatures are part of the Normalizer engine.

Configuring the IP Fragment Reassembly Mode

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

Note You can configure the IP fragment reassembly mode if your sensor is operating in promiscuous mode. If your sensor is operating inline mode, the method is NT only.

To configure the mode the sensor uses for IP fragment reassembly, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures > Advanced > Miscellaneous .

Step 3 Under Fragment Reassembly, from the IP Reassembly Mode field choose the operating system you want to use to reassemble the fragments.

Tip To discard your changes and close the Advanced dialog box, click Cancel.

Step 4 Click OK , and then Apply to apply your changes and save the revised configuration

Tip To discard your changes, click Reset.

Tuning an IP Fragment Reassembly Signature

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following procedure demonstrates how to tune an IP fragment reassembly signature, specifically, signature 1200 0 IP Fragmentation Buffer Full.

To tune an IP fragment reassembly signature, follow these steps:

Step 1 Log in to the IDM using an account with administrator or operator privileges.

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures.

Step 3 In the Filter field, choose Engine from the drop-down list, and then choose Normalizer as the engine.

Step 4 Select the IP fragment reassembly signature you want to configure in the list, for example, Sig ID 1200 Subsig ID 0 IP Fragmentation Buffer Full, and then click Edit .

Step 5 Change the default setting of any IP fragment reassembly parameters that can be configured for signature 1200. For example, in the Max Fragments field change the setting from the default of 10000 to 20000. For signature 1200, you can also change the parameters of these options:

• Specify TCP Idle Timeout
• Specify Service Ports
• Specify SYN Flood Max Embryonic

Tip To discard your changes and close the Edit Signature dialog box, click Cancel.

Step 6 Click OK , and then Apply to apply your changes and save the revised configuration

Tip To discard your changes, click Reset.

Configuring TCP Stream Reassembly Signatures

This section describes TCP stream reassembly, lists the TCP stream reassembly signatures with the configurable parameters, describes how to configure TCP stream signatures, and how to configure the mode for TCP stream reassembly. It contains the following topics:

• Understanding TCP Stream Reassembly Signatures
• TCP Stream Reassembly Signatures and Configurable Parameters
• Configuring the TCP Stream Reassembly Mode
• Tuning a TCP Stream Reassembly Signature

Understanding TCP Stream Reassembly Signatures

You can configure the sensor to monitor only TCP sessions that have been established by a complete three-way handshake. You can also configure how long to wait for the handshake to complete, and how long to keep monitoring a connection where no more packets have been seen. The goal is to prevent the sensor from creating alerts where a valid TCP session has not been established. There are known attacks against sensors that try to get the sensor to generate alerts by simply replaying pieces of an attack. The TCP session reassembly feature helps to mitigate these types of attacks against the sensor.

You configure TCP stream reassembly parameters per signature. You can configure the mode for TCP stream reassembly.

For More Information

For more information on Normalizer signature engine, see Normalizer Engine.

TCP Stream Reassembly Signatures and Configurable Parameters

Table 7-6 lists TCP stream reassembly signatures with the parameters that you can configure for TCP stream reassembly. TCP stream reassembly signatures are part of the Normalizer engine.

Configuring the TCP Stream Reassembly Mode

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

Note The parameters TCP Handshake Required and TCP Reassembly Mode only impact sensors inspecting traffic in promiscuous mode, not inline mode. To configure asymmetric options for sensors inspecting inline traffic, use the Normalizer Mode parameter.

To configure the TCP stream reassembly mode, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures > Advanced > Miscellaneous .

Step 3 Under Stream Reassembly, in TCP Handshake Required field, choose Yes . Choosing TCP Handshake Required specifies that the sensor should only track sessions for which the three-way handshake is completed.

Step 4 In the TCP Reassembly Mode field, from the drop-down list, choose the mode the sensor should use to reassemble TCP sessions:

• Asymmetric —Lets the sensor synchronize state with the flow and maintain inspection for those engines that do not require both directions.
• Strict —If a packet is missed for any reason, all packets after the missed packet are processed.
• Loose —Use in environments where packets might be dropped.

Tip To discard your changes and close the Advanced dialog box, click Cancel.

Step 5 Click OK , and then Apply to apply your changes and save the revised configuration

Tip To discard your changes, click Reset.

For More Information

For information on asymmetric inspection options for sensors configured in inline mode, see Inline TCP Session Tracking Mode and Adding, Editing, and Deleting Virtual Sensors.

Tuning a TCP Stream Reassembly Signature

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

The following procedure demonstrates how to tune a TCP stream reassembly signatures, for example, signature 1313 0 TCP MSS Exceeds Maximum.

To tune a TCP stream reassembly signature, follow these steps:

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures.

Step 3 From the Filter drop-down list, choose Engine and then choose Normalizer .

Step 4 Select the TCP fragment reassembly signature you want to configure in the list, for example, Sig ID 1313 Subsig ID 0 TCP MSS Exceeds Maximum, and click Edit .

Step 5 Change the default setting of any configurable IP fragment reassembly parameters for signature 1313. For example, in the TCP Max MSS field, change the setting from the default of 1460 to 1380. Changing this parameter from the default of 1460 to 1380 helps prevent fragmentation of traffic going through a VPN tunnel.

Step 6 For signature 1313 0, you can also change the parameters of these options:

• Specify Hijack Max Old Ack
• Specify TCP Idle Timeout
• Specify Service Ports
• Specify SYN Flood Max Embryonic

Tip To discard your changes and close the Edit Signature dialog box, click Cancel.

Step 7 Click OK , and then Apply to apply your changes and save the revised configuration

Tip To discard your changes, click Reset.

Configuring IP Logging

Tip An empty check box indicates the default value is being used. Check the check box to configure that parameter. Click the value field to change the parameter. A green check indicates that a user-defined value is being used. Click the green check to change the value back to the default.

You can configure a sensor to generate an IP session log when the sensor detects an attack. When IP logging is configured as a response action for a signature and the signature is triggered, all packets to and from the source address of the alert are logged for a specified period of time.

Note IP logging allows a maximum limit of 20 concurrent IP log files. Once the limit of 20 is reached, you receive the following message in main.log: Cid/W errWarnIpLogProcessor::addIpLog: Ran out of file descriptors

You can configure a sensor to generate an IP session log when the sensor detects an attack. When IP logging is configured as a response action for a signature and the signature is triggered, all packets to and from the source address of the alert are logged for a specified period of time.

Note IP logging allows a maximum limit of 20 concurrent IP log files. Once the limit of 20 is reached, you receive the following message in main.log: Cid/W errWarnIpLogProcessor::addIpLog: Ran out of file descriptors

When the sensor meets any one of the IP logging conditions, it stops IP logging.

To configure IP logging parameters, follow these steps:

Step 1 Log in to the IDM using an account with administrator or operator privileges.

Step 2 Choose Configuration > Policies > Signature Definitions > sig0 > Active Signatures > Advanced > Miscellaneous .

Step 3 Under IP Log in the Max IP Log Packets field, enter the maximum number of packets per log. The range is 0 to 65535. The default is 0 packets.

Step 4 In the IP Log Time field, enter the duration in seconds you want the sensor to log. A valid value is 30 to 300 seconds. The default is 30 seconds.

Step 5 In the Max IP Log Bytes field, enter the maximum size in bytes per log. The range is 0 to 2147483647 bytes. The default is 0 bytes.

Tip To discard your changes and close the Advanced dialog box, click Cancel.

Step 6 Click OK , and then Apply to apply your changes and save the revised configuration

Tip To discard your changes, click Reset.