Cisco Intrusion Prevention System Manager Express Configuration Guide for IPS 7.2

Understanding Event Action Rules

In the Event Action Rules pane, you can add, clone, or delete an event action rules policy. The default event action rules policy is rules0. 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 Event Action Rules. 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.

Calculating the Risk Rating

A risk rating (RR) is a value between 0 and 100 that represents a numerical quantification of the risk associated with a particular event on the network. The calculation takes into account the value of the network asset being attacked (for example, a particular server), so it is configured on a per-signature basis using the attack severity rating and the signature fidelity rating, and on a per-server basis using the target value rating. The risk rating is calculated from several components, some of which are configured, some collected, and some derived.

Note The risk rating is associated with alerts not signatures.

Risk ratings let you prioritize alerts that need your attention. These risk rating factors take into consideration the severity of the attack if it succeeds, the fidelity of the signature, the reputation score of the attacker from the global correlation data, and the overall value of the target host to you. The risk rating is reported in the evIdsAlert.

The following values are used to calculate the risk rating for a particular event:

• Signature fidelity rating (SFR)—A weight associated with how well this signature might perform in the absence of specific knowledge of the target. The signature fidelity rating is configured per signature and indicates how accurately the signature detects the event or condition it describes.

Signature fidelity rating is calculated by the signature author on a per-signature basis. The signature author defines a baseline confidence ranking for the accuracy of the signature in the absence of qualifying intelligence on the target. It represents the confidence that the detected behavior would produce the intended effect on the target platform if the packet under analysis were allowed to be delivered. For example, a signature that is written with very specific rules (specific regular expression) has a higher signature fidelity rating than a signature that is written with generic rules.

Note The signature fidelity rating does not indicate how bad the detected event may be.

• Attack severity rating (ASR)—A weight associated with the severity of a successful exploit of the vulnerability. The attack severity rating is derived from the alert severity parameter (informational, low, medium, or high) of the signature. The attack severity rating is configured per signature and indicates how dangerous the event detected is.

Note The attack severity rating does not indicate how accurately the event is detected.

• Target value rating (TVR)—A weight associated with the perceived value of the target.

Target value rating is a user-configurable value (zero, low, medium, high, or mission critical) that identifies the importance of a network asset (through its IP address). You can develop a security policy that is more stringent for valuable corporate resources and looser for less important resources. For example, you could assign a target value rating to the company web server that is higher than the target value rating you assign to a desktop node. In this example, attacks against the company web server have a higher risk rating than attacks against the desktop node. Target value rating is configured in the event action rules policy.

• Attack relevance rating (ARR)—A weight associated with the relevancy of the targeted operating system. Attack relevancy rating is a derived value (relevant, unknown, or not relevant), which is determined at alert time. The relevant operating systems are configured per signature.
• Promiscuous delta (PD)—A weight associated with the promiscuous delta, which can be subtracted from the overall risk rating in promiscuous mode. Promiscuous delta is in the range of 0 to 30 and is configured per signature.

Note If the trigger packet is not inline, the promiscuous delta is subtracted from the rating.

• Watch list rating (WLR)—A weight associated with the CSA MC watch list in the range of 0 to 100 (CSA MC only uses the range 0 to 35). If the attacker for the alert is found on the watch list, the watch list rating for that attacker is added to the rating.

Figure 12-1 illustrates the risk rating formula:

Figure 12-1 Risk Rating Formula

Understanding Threat Rating

Threat rating is risk rating that has been lowered by event actions that have been taken. Nonlogging event actions have a threat rating adjustment. The largest threat rating from all the event actions taken is subtracted from the risk rating. The event actions have the following threat ratings:

• Deny attacker inline—45
• Deny attacker victim pair inline—40
• Deny attacker service pair inline—40
• Deny connection inline—35
• Deny packet inline—35
• Modify packet inline—35
• Request block host—20
• Request block connection—20
• Reset TCP connection—20
• Request rate limit—20

Understanding Event Action Overrides

You can add an event action override to change the actions associated with an event based on the risk rating of that event. Event action overrides are a way to add event actions globally without having to configure each signature individually. Each event action has an associated risk rating range. If a signature event occurs and the risk rating for that event falls within the range for an event action, that action is added to the event. For example, if you want any event with a risk rating of 85 or more to generate an SNMP trap, you can set the risk rating range for Request SNMP Trap to 85-100 . If you do not want to use action overrides, you can disable the entire event action override component.

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

Understanding Event Action Filters

Event action filters are processed as an ordered list and you can move filters up or down in the list. Filters let the sensor perform certain actions in response to the event without requiring the sensor to perform all actions or remove the entire event. Filters work by removing actions from an event. A filter that removes all actions from an event effectively consumes the event.

Note When filtering sweep signatures, we recommend that you do not filter the destination addresses. If there are multiple destination addresses, only the last address is used for matching the filter.

Event Action Summarization

Summarization decreases the volume of alerts sent out from the sensor by providing basic aggregation of events into a single alert. Special parameters are specified for each signature and they influence the handling of the alerts. Each signature is created with defaults that reflect a preferred normal behavior. However, you can tune each signature to change this default behavior within the constraints for each engine type.

The nonalert-generating actions (deny, block, TCP reset) go through the filters for each signature event unsummarized. The alert-generating actions are not performed on these summarized alerts; instead the actions are applied to the one summary alert and then put through the filters.

If you select one of the other alert-generating actions and do not have it filtered out, the alert is created even if you do not select Product Alert. To prevent alerts from being created, you must have all alert-generating actions filtered out.

Summarization and event actions are processed after the Meta engine has processed the component events. This lets the sensor watch for suspicious activity transpiring over a series of events.

Event Action Aggregation

Basic aggregation provides two operating modes. The simple mode involves configuring a threshold number of hits for a signature that must be met before the alert is sent. A more advanced mode is timed-interval counting. In this mode, the sensor tracks the number of hits per second and only sends alerts when that threshold is met. In this example, a hit is a term used to describe an event, which is basically an alert, but it is not sent out of the sensor as an alert until the threshold number of hits has been exceeded.

You can choose from the following summarization options:

• Fire All—Fires an alert each time the signature is triggered. If the threshold is set for summarization, alerts are fired for each execution until summarization occurs. After summarization starts, only one alert every summary interval fires for each address set. Alerts for other address sets are either all seen or separately summarized. The signature reverts to fire all mode after a period of no alerts for that signature.
• Summary—Fires an alert the first time a signature is triggered, and then additional alerts for that signature are summarized for the duration of the summary interval. Only one alert every summary interval should fire for each address set. If the global summary threshold is reached, the signature goes into global summarization mode.
• Global Summarization—Fires an alert for every summary interval. Signatures can be preconfigured for global summarization.
• Fire Once—Fires an alert for each address set. You can upgrade this mode to global summarization mode.

Signature Event Action Processor

The Signature Event Action Processor coordinates the data flow from the signature event in the Alarm Channel to processing through the Signature Event Action Override, the Signature Event Action Filter, and the Signature Event Action Handler. It consists of the following components:

• Alarm Channel—The unit that represents the area to communicate signature events from the SensorApp inspection path to signature event handling.

• Signature Event Action Override—Adds actions based on the risk rating value. Signature Event Action Override applies to all signatures that fall in the range of the configured risk rating threshold. Each Signature Event Action Override is independent and has a separate configuration value for each action type.

• Signature Event Action Filter—Subtracts actions based on the signature ID, addresses, and risk rating of the signature event. The input to the Signature Event Action Filter is the signature event with actions possibly added by the Signature Event Action Override.

Note The Signature Event Action Filter can only subtract actions, it cannot add new actions.

The following parameters apply to the Signature Event Action Filter:

– Signature ID

– Subsignature ID

– Attacker address

– Attacker port

– Victim address

– Victim port

– Risk rating threshold range

– Actions to subtract

– Sequence identifier (optional)

– Stop-or-continue bit

– Enable action filter line bit

– Victim OS relevance or OS relevance

• Signature Event Action Handler—Performs the requested actions. The output from the Signature Event Action Handler is the actions being performed and possibly an evIdsAlert written to the Event Store.

Figure 12-2 illustrates the logical flow of the signature event through the Signature Event Action Processor and the operations performed on the action for this event. It starts with the signature event with configured action received in the Alarm Channel and flows top to bottom as the signature event passes through the functional components of the Signature Event Action Processor.

Figure 12-2 Signature Event Through Signature Event Action Processor

Event Actions

The Cisco IPS supports the following event actions. Most of the event actions belong to each signature engine unless they are not appropriate for that particular engine.

Alert and Log Actions

• Product Alert—Writes the event to the 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 There are other event actions that force a Product Alert. These actions use Product Alert as the vehicle for performing the action. Even if Product Alert is not selected or is filtered, the alert is still produced. The actions are the following: Produce Verbose Alert, Request SNMP Trap, Log Attacker Packets, Log Victim Packets, and Log Pair Packets.

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

Deny Actions

• Deny Packet Inline (inline only)—Terminates the 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)—Terminates the current packet and future packets on this 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 > sensor_name > 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)—Terminates the current packet and future packets from this 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_name > 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 IPv6 does not support Request Block Host.

Note For block actions, to set the duration of the block, choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > General Settings.

• 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 IPS modules, 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 Reset 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:

Understanding Deny Packet Inline and Reset TCP Connection

Pay attention to the following when configuring Deny Packet Inline and Reset TCP Connection:

• If you want to deny attack packets from reaching the victim and also reset the TCP connection for that flow, then you must configure BOTH Deny Packet Inline AND Reset TCP Connection.
• Configuring Reset TCP Connection alone only resets the TCP connection but the attack packet is not denied from reaching the victim.
• Configuring Deny Packet Inline alone only denies the attack packet from reaching the victim. It does not trigger a TCP reset.

For More Information

• For the procedure for configuring the general settings, see Configuring the General Settings.
• For the procedure for configuring SNMP, see Chapter18, “Configuring SNMP”
• For the procedure for configuring denied attackers, see Configuring and Monitoring Denied Attackers.

Event Action Rules Pane

Note You must be administrator or operator to add, clone, or delete event action rules policies.

In the Event Action Rules pane, you can add, clone, or delete an event action rules policy. The default event action rules policy is rules0. 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 Event Action Rules. 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.

Event Action Rules Pane Field Definitions

The following fields are found in the Event Action Rules pane:

• Policy Name—Identifies the name of this event action rules policy.
• Assigned Virtual Sensor—Identifies the virtual sensor for which this event action rules policy is assigned.

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 Event Action Rules Policies

To add, clone, or delete an event action rules policy, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules , and then click Add .

Step 3 In the Policy Name field, enter a name for the event action rules policy.

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

Step 4 Click OK . The event action rules policy appears in the list in the Event Action Rules pane.

Step 5 To clone an existing event action rules policy, select it in the list, and then click Clone . The Clone Policy dialog box appears with “_copy” appended to the existing event action rules policy name.

Step 6 In the Policy Name field, enter a unique name.

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

Step 7 Click OK . The cloned event action rules policy appears in the list in the Event Action Rules pane.

Step 8 To remove an event action rules 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 9 Click Yes . The event action rules policy no longer appears in the list in the Event Action Rules pane.

Event Action Overrides Tab

Note You must be administrator or operator to add or edit event action overrides.

On the Event Action Overrides tab, you can add an event action override to change the actions associated with an event based on specific details about that event.

Event Action Overrides Tab Field Definitions

The following fields are found on the Event Action Overrides tab:

• Use Event Action Overrides—If checked, lets you use any event action override that is enabled.
• Risk Rating—Indicates the risk rating level that should be used to trigger this event action override.

If an event occurs with a risk rating that matches this level, the event action is added to this event.

• Actions to Add—Specifies the event action that will be added to an event if the conditions of this event action override are satisfied.
• Enabled—Indicates whether or not the override is enabled.

Add and Edit Event Action Override Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Event Action Override dialog boxes:

• Risk Rating—Indicates the risk rating range, either low, medium, or high risk, that should be used to trigger this event action override. If an event occurs with a risk rating that corresponds to the risk you configure, the event action is added to this event.
• Available Actions to Add—Specifies the event action that will be added to an event if the conditions of this event action override are satisfied.
• Enabled—Check the check box to enable the action when the event action override is triggered.

Adding, Editing, Deleting, Enabling, and Disabling Event Action Overrides

To add, edit, delete, enable, and disable event action overrides, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > Event Action Overrides .

Step 3 To create a event action override, click Add .

Step 4 From the Risk Rating drop-down menu, assign a risk rating range to this network asset.

Step 5 From the Available Actions to Add list, check the event actions to which this event action override will correspond.

Step 6 Check the Enabled check boxes for the actions you want to enable in the override.

Tip To discard your changes and close the Add Event Action Override dialog box, click Cancel.

Step 7 Click OK . The new event action override now appears in the list on the Event Action Overrides tab.

Step 8 Check the Use Event Action Overrides check box.

Note You must check the Use Event Action Overrides check box on the Event Action Overrides tab or none of the event action overrides will be enabled regardless of the value you set.

Step 9 To edit an existing event action override, select it in the list, and then click Edit . Make any changes needed.

Tip To discard your changes and close the Edit Event Action Override dialog box, click Cancel.

Step 10 Click OK . The edited event action override now appears in the list on the Event Action Overrides tab.

Step 11 Check the Use Event Action Overrides check box.

Note You must check the Use Event Action Overrides check box on the Event Action Overrides tab or none of the event action overrides will be enabled regardless of the value you set.

Step 12 To delete an event action override, select it in the list, and then click Delete . The event action override no longer appears in the list on the Event Action Overrides tab.

Step 13 To enable or disable an event action override, select it in the list, and then click Edit .

Step 14 To disable an event action override, clear the Enabled check boxes for any event actions that you have assigned to that event action override. To enable an event action override, check any Enabled check boxes for any event actions that you have assigned to that event action override.

Tip To discard your changes, click Reset.

Step 15 Click Apply to apply your changes and save the revised configuration.

Event Action Filters Tab

Note You must be administrator or operator to add, edit, enable, disable, or delete event action filters.

You can configure event action filters to remove specific actions from an event or to discard an entire event and prevent further processing by the sensor. You can use the variables that you defined on the Event Variables pane to group addresses for your filters.

You must preface the variable with a dollar sign ($) to indicate that you are using a variable rather than a string. Otherwise, you receive the Bad source and destination error.

Event Action Filters Tab Field Definitions

The following fields are found on the Event Action Filters tab:

• Name—Lets you name the filter you are adding. You need to name your filters so that you can move them around in the list and move them to the inactive list if needed.
• Enabled—Indicates whether or not this filter is enabled.
• Sig ID—Identifies the unique numerical value assigned to this signature. This value lets the sensor identify a particular signature. You can also enter a range of signatures.
• SubSig ID—Identifies the unique numerical value assigned to this subsignature. The subSig ID identifies a more granular version of a broad signature. You can also enter a range of subSig IDs.
• Attacker (IPv4/IPv6/port)—Identifies the IP address and/or port of the host that sent the offending packet. You can also enter a range of addresses or ports.
• Victim (IPv4/IPv6/port)—Identifies the IP address and/or port used by the attacker host. You can also enter a range of addresses or ports.
• Risk Rating—Indicates the risk rating range between 0 and 100 that should be used to trigger this event action filter. If an event occurs with an risk rating that falls within the minimum-maximum range you configure here, the event is processed against the rules of this event filter.
• Actions to Subtract—Indicates the actions that should be removed from the event, should the conditions of the event meet the criteria of the event action filter.

Add and Edit Event Action Filter Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Event Action Filter dialog boxes:

• Name—Lets you name the filter you are adding. You need to name your filters so that you can move them around in the list and move them to the inactive list if needed.
• Enabled—Lets you enable this filter.
• Signature ID—Identifies the unique numerical value assigned to this signature. This value lets the sensor identify a particular signature. You can also enter a range of signatures.
• Subsignature ID—Identifies the unique numerical value assigned to this subsignature. The subsignature ID identifies a more granular version of a broad signature. You can also enter a range of subsignature IDs.
• Attacker IPv4 Address—Identifies the IP address of the host that sent the offending packet. You can also enter a range of addresses.

• Attacker IPv6 Address—Identifies the range set of attacker IPv6 addresses of the host that sent the offending packet in the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Example—2001:0db8:1234:1234:1234:1234:1234:1234,2001:0db8:1234:1234:1234:1234:1234:8888. The second IPv6 address in the range must be greater than or equal to the first IPv6 address.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

• Attacker Port—Identifies the port used by the attacker host. This is the port from where the offending packet originated. You can also enter a range of ports.
• VictimIPv4 Address—Identifies the IP address of the host being attacked (the recipient of the offending packet). You can also enter a range of addresses.

• VictimIPv6 Address—Identifies the range set of victim IPv6 addresses of the host that is the being attacked (the recipient of the offending packet) in the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Example—2001:0db8:1234:1234:1234:1234:1234:1234,2001:0db8:1234:1234:1234:1234:1234:8888. The second IPv6 address in the range must be greater than or equal to the first IPv6 address.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

• Victim Port—Identifies the port through which the offending packet was received. You can also enter a range of ports.
• Risk Rating—Indicates the risk rating range between 0 and 100 that should be used to trigger this event action filter. If an event occurs with a risk rating that falls within the minimum-maximum range you configure here, the event is processed against the rules of this event filter.
• Actions to Subtract—Opens the Edit Actions dialog box and lets you choose the actions that should be removed from the event, should the conditions of the event meet the criteria of the event action filter.

• More Options

– Active—Lets you add the filter to the filter list so that it takes effect on filtering events.

– OS Relevance—Lets you filter out events where the attack is not relevant to the victim operating system.

– Deny Percentage—Determines the percentage of packets to deny for deny attacker features. The valid range is 0 to 100. The default is 100 percent.

– Stop on Match—Determines whether or not this event will be processed against remaining filters in the event action filters list. If set to No, the remaining filters are processed for a match until a Stop flag is encountered. If set to Yes, no further processing is done. The actions specified by this filter are removed and the remaining actions are performed.

– Comments—Displays the user comments associated with this filter.

Adding, Editing, Deleting, Enabling, Disabling, and Moving Event Action Filters

To add, edit, delete, enable, disable, and move event action filters, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > Event Action Filters , and then click Add .

Step 3 In the Name field, enter a name for the event action filter. A default name is supplied, but you can change it to a more meaningful name.

Step 4 In the Enabled field, click the Yes radio button to enable the filter.

Step 5 In the Signature ID field, enter the signature IDs of all signatures to which this filter should be applied. You can use a list (2001, 2004), or a range (2001–2004), or one of the SIG variables you defined on the Event Variables tab. Preface the variable with $.

Step 6 In the SubSignature ID field, enter the subsignature IDs of the subsignatures to which this filter should be applied.

Step 7 In the Attacker IPv4 Address field, enter the IP address of the source host. You can use a variable you defined on the Event Variables tab. Preface the variable with $. You can also enter a range of addresses (for example, 0.0.0.0-255.255.255.255).

Step 8 In the Attacker IPv6 Address field, enter the range set of attacker IPv6 addresses of the source host in the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>].

The second IPv6 address in the range must be greater than or equal to the first IPv6 address. You can also use a variable you defined on the Event Variables tab. Preface the variable with $.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

Step 9 In the Attacker Port field, enter the port number used by the attacker to send the offending packet.

Step 10 In the Victim IPv4 Address field, enter the IP address of the recipient host. You can use one of the variables if you defined them on the Event Variables tab. Preface the variable with $. You can also enter a range of addresses (for example, 0.0.0.0-255.255.255.255).

Step 11 In the Victim IPv6 Address field, enter the range set of IPv6 address of the recipient host in the following format.

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>].

The second IPv6 address in the range must be greater than or equal to the first IPv6 address. You can use a variable you defined on the Event Variables tab. Preface the variable with $.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

Step 12 In the Victim Port field, enter the port number used by the victim host to receive the offending packet.

Step 13 In the Risk Rating field, enter a risk rating range for this filter. If the risk rating for an event falls within the range you specify, the event is processed against the criteria of this filter.

Step 14 In the Actions to Subtract field, click the note icon to open the Edit Actions dialog box. Check the check boxes of the actions you want this filter to remove from the event.

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

Step 15 In the Active field, click the Yes radio button to add this filter to the list so that it takes effect on filtering events.

Step 16 In the OS Relevance drop-down list, choose whether you want to know if the alert is relevant to the operating system that has been identified for the victim.

Step 17 In the Deny Percentage field, enter the percentage of packets to deny for deny attacker features. The default is 100 percent.

Step 18 In the Stop on Match field, click one of the following radio buttons:

a. Yes —If you want the Event Action Filters component to stop processing after the actions of this particular filter have been removed. Any remaining filters will not be processed; therefore, no additional actions can be removed from the event.

b. No —If you want to continue processing additional filters.

Step 19 In the Comments field, enter any comments that you want to store with this filter, such as the purpose of this filter or why you have configured this filter in a particular way.

Tip To discard your changes and close the Add Event Action Filter dialog box, click Cancel.

Step 20 Click OK . The new event action filter now appears in the list on the Event Action Filters tab.

Step 21 To edit an existing event action filter, select it in the list, and then click Edit .

Step 22 Make any changes needed.

Tip To discard your changes and close the Edit Event Action Filter dialog box, click Cancel.

Step 23 Click OK . The edited event action filter now appears in the list on the Event Action Filters tab.

Step 24 To delete an event action filter, select it in the list, and then click Delete . The event action filter no longer appears in the list on the Event Action Filters tab.

Step 25 To move an event action filter up or down in the list, select it, and then click the Move Up or Move Down arrow icons.

Tip To discard your changes, click Reset.

Step 26 Click Apply to apply your changes and save the revised configuration.

IPv4 Target Value Rating Tab

Note You must be administrator or operator to add, edit, or delete target value ratings.

You can assign a target value rating to your network assets. The target value rating is one of the factors used to calculate the risk rating value for each alert. You can assign different target value ratings to different targets. Events with a higher risk rating trigger more severe signature event actions.

IPv4 Target Value Rating Tab Field Definitions

The following fields are found on the IPv4 Target Value Rating tab:

• Target Value Rating (TVR)—Identifies the value assigned to this network asset. The value can be High, Low, Medium, Mission Critical, or No Value.

• Target IP Address—Identifies the IP address of the network asset you want to prioritize with a target value rating.

Add and Edit Target Value Rating Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Target Value Rating dialog boxes:

• Target Value Rating (TVR)—Lets you assign a value to this network asset. The value can be High, Low, Medium, Mission Critical, or No Value.

• Target IPv4 Address(es)—Identifies the IP address of the network asset you want to prioritize with a target value rating.

Adding, Editing, and Deleting IPv4 Target Value Ratings

To add, edit, and delete the IPv4 target value rating for network assets, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > IPv4 Target Value Rating , and then click Add .

Step 3 To assign a target value rating to a new group of assets, follow these steps:

a. From the Target Value Rating (TVR) drop-down list, choose a rating. The values are High, Low, Medium, Mission Critical, or No Value.

b. In the Target IPv4 Address(es) field, enter the IP address of the network asset. To enter a range of IP addresses, enter the lowest address followed by a hyphen and then the highest address in the range. For example: 10.10.2.1-10.10.2.30.

Tip To discard your changes and close the Add Target Value Rating dialog box, click Cancel.

Step 4 Click OK . The new target value rating for the new asset appears in the list on the IPv4 Target Value Rating tab.

Step 5 To edit an existing target value rating, select it in the list, and then click Edit .

Step 6 Make any changes needed.

Tip To discard your changes and close the Edit Target Value Rating dialog box, click Cancel.

Step 7 Click OK . The edited network asset now appears in the list on the IPv4 Target Value Rating tab.

Step 8 To delete a network asset, select it in the list, and then click Delete . The network asset no longer appears in the list on the Ipv4 Target Value Rating tab.

Tip To discard your changes, click Reset.

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

IPv6 Target Value Rating Tab

Note You must be administrator or operator to add, edit, or delete target value ratings.

You can assign a target value rating to your network assets. The target value rating is one of the factors used to calculate the risk rating value for each alert. You can assign different target value ratings to different targets. Events with a higher risk rating trigger more severe signature event actions.

IPv6 Target Value Rating Tab Field Definitions

The following fields are found on the IPv6 Target Value Rating tab:

• Target Value Rating (TVR)—Identifies the value assigned to this network asset. The value can be High, Low, Medium, Mission Critical, or No Value.

• Target IP Address—Identifies the IP address of the network asset you want to prioritize with a target value rating.

Add and Edit IPv6 Target Value Rating Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Target Value Rating dialog boxes:

• Target Value Rating (TVR)—Lets you assign a value to this network asset. The value can be High, Low, Medium, Mission Critical, or No Value.

• Target IPv6 Address(es)—Identifies the IPv6 address of the network asset you want to prioritize with a target value rating in the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Example—2001:0db8:1234:1234:1234:1234:1234:1234,2001:0db8:1234:1234:1234:1234:1234:8888. The second IPv6 address in the range must be greater than or equal to the first IPv6 address.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

Adding, Editing, and Deleting IPv6 Target Value Ratings

To add, edit, and delete the IPv6 target value rating for network assets, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > IPv6 Target Value Rating , and then click Add .

Step 3 To assign a target value rating to a new group of assets, follow these steps:

a. From the Target Value Rating (TVR) drop-down list, choose a rating. The values are High, Low, Medium, Mission Critical, or No Value.

b. In the Target IPv6 Address(es) field, enter the IP address of the network asset.

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>].

You can also use a variable you defined on the Event Variables tab. Preface the variable with $. The second IPv6 address in the range must be greater than or equal to the first IPv6 address.

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

Tip To discard your changes and close the Add Target Value Rating dialog box, click Cancel.

Step 4 Click OK . The new target value rating for the new asset appears in the list on the IPv6 Target Value Rating tab.

Step 5 To edit an existing target value rating, select it in the list, and then click Edit .

Step 6 Make any changes needed.

Tip To discard your changes and close the Edit Target Value Rating dialog box, click Cancel.

Step 7 Click OK . The edited network asset now appears in the list on the IPv6 Target Value Rating tab.

Step 8 To delete a network asset, select it in the list, and then click Delete . The network asset no longer appears in the list on the IPv6 Target Value Rating tab.

Tip To discard your changes, click Reset.

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

OS Identifications Tab

Note You must be administrator or operator to add, edit, and delete configured OS maps.

Use the OS Identifications tab to configure OS host maps, which take precedence over learned OS maps. On the OS Identifications tab you can add, edit, and delete configured OS maps. You can move them up and down in the list to change the order in which the sensor computes the attack relevance rating and risk rating for that particular IP address and OS type combination.

You can also move OS maps up and down in the list to change the order in which the sensor resolves the OS associated with a particular IP address. Configured OS maps allow for ranges. More specific maps should be at the beginning of the list. Overlap in the IP address range sets is allowed, but the entry closest to the beginning of the list takes precedence. For example, for network 192.168.1.0/24 an administrator might define the following ( Table 12-1 ):

Understanding Passive OS Fingerprinting

Passive OS fingerprinting lets the sensor determine the OS that hosts are running. The sensor analyzes network traffic between hosts and stores the OS of these hosts with their IP addresses. The sensor inspects TCP SYN and SYNACK packets exchanged on the network to determine the OS type.

The sensor then uses the OS of the target host OS to determine the relevance of the attack to the victim by computing the attack relevance rating component of the risk rating. Based on the relevance of the attack, the sensor may alter the risk rating of the alert for the attack and/or the sensor may filter the alert for the attack. You can then use the risk rating to reduce the number of false positive alerts (a benefit in IDS mode) or definitively drop suspicious packets (a benefit in IPS mode). Passive OS fingerprinting also enhances the alert output by reporting the victim OS, the source of the OS identification, and the relevance to the victim OS in the alert.

Passive OS fingerprinting consists of three components:

• Passive OS learning—Passive OS learning occurs as the sensor observes traffic on the network. Based on the characteristics of TCP SYN and SYNACK packets, the sensor makes a determination of the OS running on the host of the source IP address.

• User-configurable OS identification—You can configure OS host maps, which take precedence over learned OS maps.
• Computation of attack relevance rating and risk rating—The sensor uses OS information to determine the relevance of the attack signature to the targeted host. The attack relevance is the attack relevance rating component of the risk rating value for the attack alert. The sensor uses the OS type reported in the host posture information imported from the CSA MC to compute the attack relevance rating.

There are three sources of OS information. The sensor ranks the sources of OS information in the following order:

1. Configured OS maps—OS maps you enter. Configured OS maps reside in the event action rules policy and can apply to one or many virtual sensors.

Note You can specify multiple operating systems for the same IP address. The last one in the list is the operating system that is matched.

2. Imported OS maps—OS maps imported from an external data source. Imported OS maps are global and apply to all virtual sensors.

Note Currently the CSA MC is the only external data source.

3. Learned OS maps—OS maps observed by the sensor through the fingerprinting of TCP packets with the SYN control bit set. Learned OS maps are local to the virtual sensor that sees the traffic.

When the sensor needs to determine the OS for a target IP address, it consults the configured OS maps. If the target IP address is not in the configured OS maps, the sensor looks in the imported OS maps. If the target IP address is not in the imported OS maps, the sensor looks in the learned OS maps. If it cannot find it there, the sensor treats the OS of the target IP address as unknown.

Note Passive OS fingerprinting is enabled by default and the IPS contains a default vulnerable OS list for each signature.

Configuring Passive OS Fingerprinting

You do not have to configure passive OS fingerprinting for it to function. IPS provides a default vulnerable OS list for each signature and passive analysis is enabled by default.

You can configure the following aspects of passive OS fingerprinting:

• Define OS maps—We recommend configuring OS maps to define the identity of the OS running on critical systems. It is best to configure OS maps when the OS and IP address of the critical systems are unlikely to change.

• Limit the attack relevance rating calculation to a specific IP address range—This limits the attack relevance rating calculations to IP addresses on the protected network.
• Import OS maps—Importing OS maps provides a mechanism for accelerating the learning rate and fidelity of the OS identifications made through passive analysis. If you have an external product interface, such as the CSA MC, you can import OS identifications from it.
• Define event action rules filters using the OS relevance value of the target—This provides a way to filter alerts solely on OS relevance.
• Disable passive analysis—Stops the sensor from learning new OS maps.
• Edit signature vulnerable OS lists—The vulnerable OS list specifies what OS types are vulnerable to each signature. The default, General OS, applies to all signatures that do not specify a vulnerable OS list.

OS Identifications Tab Field Definitions

The following fields are found on the OS Identifications tab:

• Enable passive OS fingerprinting analysis—When checked, lets the sensor perform passive OS analysis.
• Restrict Attack Relevance Ratings (ARR) to these IP addresses—Lets you configure the mapping of OS type to a specific IP address and have the sensor calculate the attack relevance rating for that IP address.
• Configured OS Maps—Displays the attributes of the configured OS maps:

– Name—Specifies the name you give the configured OS map.

– Active—Whether this configured OS map is active or inactive.

– IP Address—Specifies the IP address of this configured OS map.

– OS Type—Specifies the OS type of this configured OS map.

Add and Edit Configured OS Map Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Configured OS Map dialog boxes:

• Name—Specifies the name of this configured OS map.
• Active—Lets you choose to make the configured OS map active or inactive.
• IP Address—Specifies the IP address associated with this configured OS map. The IP address for configured OS maps (and only configured OS maps) can be a set of IP addresses and IP address ranges. The following are all valid IP address values for configured OS maps:

– 10.1.1.1,10.1.1.2,10.1.1.15

– 10.1.2.1

– 10.1.1.1-10.2.1.1,10.3.1.1

– 10.1.1.1-10.1.1.5

• OS Type—Lets you choose one of the following OS types to associate with the IP address:

– AIX

– BSD

– General OS

– HP UX

– IOS

– IRIX

– Linux

– Mac OS

– Netware

– Other

– Solaris

– UNIX

– Unknown OS

– Win NT

– Windows

– Windows NT/2K/XP

Adding, Editing, Deleting, and Moving Configured OS Maps

To add, edit, delete, and move configured OS maps, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > OS Identifications , and then click Add .

Step 3 In the Name field, enter a name for the configured OS map.

Step 4 In the Active field, click the Yes radio button to add this configured OS map to the list so that it takes effect.

Step 5 In the IP Address field, enter the IP address of the host that you are mapping to an OS. For example, use this format, 10.10.5.5,10.10.2.1-10.10.2.30.

Step 6 From the OS Type drop-down list, choose the OS that will be mapped to the IP address.

Tip To discard your changes and close the Add Configured OS Map dialog box, click Cancel.

Step 7 Click OK . The new configured OS map now appears in the list on the OS Identifications tab.

Step 8 Check the Enable passive OS fingerprinting analysis check box.

Note You must check the Enable passive OS fingerprinting analysis check box on the OS Identifications tab or none of the configured OS maps will be enabled regardless of the value you set in the Add Configured OS Map dialog box.

Step 9 To edit a configured OS map, select it in the list, and then click Edit .

Step 10 Make any changes needed.

Tip To discard your changes and close the Edit Configured OS Map dialog box, click Cancel.

Step 11 Click OK . The edited configured OS map now appears in the list on the OS Identifications tab.

Step 12 Check the Enable passive OS fingerprinting analysis check box.

Note You must check the Enable passive OS fingerprinting analysis check box on the OS Identifications tab or none of the configured OS maps will be enabled regardless of the value you set in the Edit Configured OS Map dialog box.

Step 13 To delete a configured OS map, select it in the list, and then click Delete . The configured OS map no longer appears in the list on the OS Identifications tab.

Step 14 To move a configured OS map up or down in the list, select it, and then click the Move Up or Move Down arrows.

Tip To discard your changes, click Reset.

Step 15 Click Apply to apply your changes and save the revised configuration.

Event Variables Tab

Note You must be administrator or operator to add, edit, or delete event variables.

You can create event variables and then use those variables in event action filters. When you want to use the same value within multiple filters, use a variable. When you change the value of the variable, any filter that uses that variable is updated with the new value.

Note You must preface the event 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.

IPv4 Addresses

When configuring IPv4 addresses, specify the full IP address or ranges or set of ranges:

• 192.0.2.3-192.0.2.26
• 10.90.1.1
• 192.56.10.1-192.56.10.255
• 10.1.1.1-10.2.255.255, 192.0.2.3-192.0.2.26

IPv6 Addresses

When configuring IPv6 addresses, use the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

Timesaver If you have an IP address space that applies to your engineering group and there are no Windows systems in that group, and you are not worried about any Windows-based attacks to that group, you could set up a variable to be the IP address space of the engineering group. You could then use this variable to configure a filter that would ignore all Windows-based attacks for this group.

Event Variables Tab Field Definitions

The following fields are found on the Event Variables tab:

• Name—Lets you assign a name to this variable.

• Type—Identifies the variable as an address.
• Value—Lets you add the value(s) represented by this variable.

Add and Edit Event Variable Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Event Variable dialog boxes:

• Name—Lets you assign a name to this variable.

• Type—Identifies the variable as an IPv4 or IPv6 address:

– address—For IPv4 address use a full IP address or range or set of ranges.

– ipv6-address—For IPv6 address use the following format: <XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

• Value—Lets you add the value(s) represented by this variable.

Adding, Editing, and Deleting Event Variables

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

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > Event Variables , and then click Add .

Step 3 In the Name field, enter a name for this variable.

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

Step 4 From the Type drop-down list, choose address for an IPv4 address or ipv6-address for an IPv6 address.

Step 5 In the Value field, enter the values for this variable.

For IPv4 addresses, specify the full IP address or ranges or set of ranges. For example:

• 10.89.10.10-10.89.10.23
• 10.90.1.1
• 192.56.10.1-192.56.10.255

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

For IPv6 address, use the following format:

<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>[,<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>-<XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX>]

Note IPv6 addresses are 128 bits represented in hexadecimal and divided into eight 16-bit groups separated by colons. You can skip the leading zeros and you can represent the zeroed groups in the middle with a double colon (::). You must start the address with the 2001:db8 prefix.

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

Step 6 Click OK . The new variable appears in the list on the Event Variables tab.

Step 7 To edit an existing variable, select it in the list, and then click Edit .

Step 8 Make any changes needed.

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

Step 9 Click OK . The edited event variable now appears in the list on the Event Variables tab.

Step 10 To delete an event variable, select it in the list, and then click Delete . The event variable no longer appears in the list on the Event Variables tab.

Tip To discard your changes, click Reset.

Step 11 Click Apply to apply your changes and save the revised configuration.

Risk Category Tab

Note You must be administrator to add and edit risk levels.

On the Risk Category tab, you can use predefined risk categories (HIGHRISK, MEDIUMRISK, AND LOWRISK) or you can define your own labels. Risk categories link a category name to a numeric range defining the risk rating. You specify the low threshold for the category to make sure that the ranges are contiguous. The upper category is either the next higher category or 100.

Note You cannot delete a predefined risk category.

Risk Category Tab Field Definitions

The following fields are found on the Risk Category tab:

• Risk Category Name—Specifies the name of this risk level. The predefined categories have the following values:

– HIGHRISK—90 (means 90 to 100)

– MEDIUMRISK—70 (means 70-89)

– LOWRISK—1 (means 1-69)

• Risk Threshold—Specifies the threshold number for this risk. The value is a number from 0 to 100.
• Risk Range—Specifies the risk rating range for this risk category. The risk rating is a range between 0 and 100 that represents a numerical quantification of the risk associated with a particular event on the network.

Add and Edit Risk Level Dialog Boxes Field Definitions

The following fields are found in the Add and Edit Risk Level dialog boxes:

• Risk Name—Specifies the name of this risk level.
• Risk Threshold—Lets you assign a risk threshold for this risk level. You specify or change only the lower threshold for the category so that the risk categories are contiguous. The upper threshold is either the next higher category or 100.
• Active—Lets you make this risk level active.

Adding, Editing, and Deleting Risk Categories

To add, edit, and delete risk categories, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > Risk Category , and then click Add .

Step 3 In the Risk Name field, enter a name for this risk category.

Step 4 In the Risk Threshold field, enter a numerical value for the risk threshold (minimum 0, maximum 100). This number represents the lower boundary of risk. The range appears in the Risk Range field and in the red, yellow, and green threshold fields.

Step 5 To make this risk category active, click the Yes radio button.

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

Step 6 Click OK . The new risk category appears in the list on the Risk Category tab.

Step 7 To edit an existing risk category, select it in the list, and then click Edit .

Step 8 Make any changes needed.

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

Step 9 Click OK . The edited risk category now appears in the list on the Risk Category tab.

Step 10 To delete a risk category, select it in the list, and then click Delete . The risk category no longer appears in the list on the Risk Category tab.

Tip To discard your changes, click Reset.

Step 11 Click Apply to apply your changes and save the revised configuration.

General Tab

Note You must be administrator or operator to configure the general settings for event action rules.

You can configure the general settings that apply globally to event action rules, such as whether you want to use the Summarizer and the Meta Event Generator. The Summarizer groups events into a single alert, thus decreasing the number of alerts the sensor sends out. The Meta Event Generator processes the component events, which lets the sensor watch for suspicious activity transpiring over a series of events.

You can also use threat rating adjustment, event action filters, and you can enable one-way TCP reset. The one-way TCP reset operates for inline mode only and is an automatic addition to the deny packet inline actions. It sends a TCP reset to the victim of the alert, thus creating a black hole for the attacker and clearing the TCP resources of the victim.

Note An inline sensor now denies packets for any alert with a risk rating of greater than or equal to 90. It also issues a one-way TCP reset on TCP alerts with a risk rating of greater than or equal to 90.

You can configure how long you want to deny attackers, the maximum number of denied attackers, and how long you want blocks to last.

General Tab Field Definitions

The following fields are found the on the General tab:

• Use Summarizer—Enables the Summarizer component. By default, the Summarizer is enabled. If you disable it, all signatures are set to Fire All with no summarization. If you configure individual signatures to summarize, this configuration will be ignored if the Summarizer is not enabled.

• Use Meta Event Generator—Enables the Meta Event Generator. By default, the Meta Event Generator is enabled. If you disable the Meta Event Generator, all Meta engine signatures are disabled.

• Use Threat Rating Adjustment—Enables threat rating adjustment, which adjusts the risk rating. If disabled, then risk rating is equal to threat rating. Use Event Action Filters—Enables the event action filter component. You must check this check box to use any filter that is enabled.
• Enable One Way TCP Reset (inline only)—Enables a one-way TCP reset for deny packet inline actions for TCP-based alerts. It sends a TCP reset to the victim of the alert thus clearing the TCP resources of the victim.
• Deny Attacker Duration—Specifies the number of seconds to deny the attacker inline. The valid range is 0 to 518400. The default is 3600.
• Block Action Duration—Specifies the number of minutes to block a host or connection. The valid range is 0 to 10000000. The default is 30.
• Maximum Denied Attackers—Specifies the limit of the number of denied attackers possible in the system at any one time. The valid range is 0 to 100000000. The default is 10000.

Configuring the General Settings

To configure the general settings for event action rules, follow these steps:

Step 2 Choose Configuration > sensor_name > Policies > Event Action Rules > rules0 > General .

Step 3 To enable the summarizer feature, check the Use Summarizer check box.

Step 4 To enable the meta event generator, check the Use Meta Event Generator check box.

Step 5 To enable threat rating adjustment, check the Use Threat Rating Adjustment check box.

Step 6 To enable event action filters, check the Use Event Action Filters check box.

Note You must check the Use Event Action Filters check box on the General pane so that any event action filters you configured in the Configuration > sensor_name > Policies > Event Action Rules > rules0 > Event Action Filters pane are active.

Step 7 To enable one way TCP reset for deny packet inline actions, check the Enable One Way TCP Reset check box.

Step 8 In the Deny Attacker Duration field, enter the number of seconds you want to deny the attacker inline.

Step 9 In the Block Action Duration field, enter the number of minutes you want to block a host or connection.

Step 10 In the Maximum Denied Attackers field, enter the maximum number of denied attackers you want at any one time.

Tip To discard your changes, click Reset.

Step 11 Click Apply to apply your changes and save the revised configuration.

For More Information

• For detailed information about threat rating, see Understanding Threat Rating.
• For detailed information about risk rating, see Calculating the Risk Rating.