Table Of Contents

Monitoring Network Traffic and Extracting Attack Signatures

Understanding Packet-Dump Capture

Enabling Automatic Packet-Dump Capture

Disabling Automatic Packet-Dump Capture

Activating Manual Packet-Dump Captures

Starting a Manual Packet-Dump Capture

Stopping a Manual Packet-Dump Capture

Viewing Packet-Dump Captures

Viewing the Packet-Dump Capture List

Viewing the Packet-Dump Capture Details

Changing the Packet-Dump Capture Details Screen View

Comparing Two Packet-Dump Captures

Managing Packet-Dump Capture Files

Renaming a Manual Packet-Dump Capture File

Copying a Packet-Dump Capture File

Exporting Packet-Dump Capture Files

Importing Packet-Dump Capture Files

Deleting Packet-Dump Capture Files

Extracting and Using Signatures from Packet-Dump Captures

Extracting an Attack Signature from a Packet-Dump Capture

Adding an Attack Signature to a Flex-Content Filter

Using an Attack Signature as a Display Pattern for Displaying Packet-Dump Captures

Monitoring Network Traffic and Extracting Attack Signatures

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This chapter describes how to record and observe zone traffic patterns by using the packet-dump capture function, which provides nonintrusive network taps.

This chapter contains the following sections:

•Understanding Packet-Dump Capture

•Enabling Automatic Packet-Dump Capture

•Disabling Automatic Packet-Dump Capture

•Activating Manual Packet-Dump Captures

•Viewing Packet-Dump Captures

•Managing Packet-Dump Capture Files

•Extracting and Using Signatures from Packet-Dump Captures

Understanding Packet-Dump Capture

You can configure the Cisco Guard (Guard) to record traffic directly from the network through nonintrusive taps and create a database from the recorded traffic. By querying the recorded traffic database, you can analyze past events, generate signatures of an attack, or compare current network traffic patterns with traffic patterns that the Guard recorded previously under normal traffic conditions.

You can configure filters so that the Guard records only traffic that meets certain criteria or you can record all traffic data and filter the traffic information that the Guard displays.

The Guard saves the traffic in a PCAP format, which is compressed and encoded by the gzip (GNU zip) program with an accompanying file in an Extensible Markup Language (XML) format that describes the recorded data.

From the recorded traffic, you can determine if there are any common patterns or signatures that appear in the payload of the attack packets. The Guard can analyze the recorded traffic and extract a signature, which you can use to configure a flex-content filter to block all traffic containing the packet payloads that match the signature.

The Guard can record the traffic as follows:

•Automatically—Continuously records traffic data in packet-dump capture files.

•Manually—Records traffic in packet-dump capture files when you activate a recording session.

New packet-dump capture files replace previously recorded capture files. To save a previously recorded capture file, export the file to a network server before you activate a new recording session.

You can activate only one manual packet-dump capture at a time for a zone, but you can activate the manual packet-dump capture and the automatic packet-dump capture simultaneously. The Guard can perform manual recording sessions for up to 10 zones simultaneously.

The Guard allocates, by default, 5-GB disk space for the manual packet-dump capture files of all zones. It can save up to 50 GB of manual and automatic packet-dump capture files of all zones. You must delete old files to free the disk space for additional packet-dump capture files.

Enabling Automatic Packet-Dump Capture

You can activate the Guard to automatically record network traffic for troubleshooting network problems or analyzing attack traffic. You can also record all traffic and apply packet-dump capture filters to the recorded traffic when you view it.

The Guard records traffic in a capture buffer. When the capture buffer size reaches 50 MB, or after 10 minutes have elapsed, the Guard saves the buffered information to a local file in a compressed format, clears the buffer, and then continues recording traffic.

The Guard can create up to three different types of capture files during the capture time period, depending on which of the following ways it handles the packets:

•Forwarded: Source IP addresses of the legitimate traffic that the Guard forwarded to the zone.

•Dropped: Source IP addresses of the malicious traffic that the Guard dropped.

•Replied: Destination IP addresses of the traffic that the Guard anti-spoofing and anti-zombie functions sent back to the source in a verification attempt.

When only a forwarded packet-dump capture file exists, it indicates that the zone was not under attack during the time of the capture. An attack on the zone is indicated when the Guard also creates dropped and replied capture files. Within each of the three types of packet-dump capture files, the Guard provides an IP summarization, which is a summary of the most frequently detected IP addresses (according to the volume of traffic).

The IP summarization information that the Guard presents in a replied packet-dump capture file enables you to determine the source of a spoofed attack. The Guard also pulls this information from the capture file and displays it in the zone attack report under the heading Replied IP Summarization (see the"Understanding the Replied IP Summarization Information" section in Chapter 10, "Monitoring Guard and Zone Operations").

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Caution To ensure accurate replied IP summarization results, you must leave the packet dump capture function enabled during the length of the attack on the zone. If you disable the packet-dump capture function during the attack, the replied IP summarization information may not display or may not be accurate. The Guard can display replied IP summarization information in the attack report only when you have the packet-dump automatic capture function enabled (no replied IP summarization information displays for manually activated packet-pump captures).

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Note The IP summarization process is resource consuming. When resources become low, the Guard suspends the process and issues a log message that appears in the zone log. The capture xml file will contain a status attribute that states that the capture file has no IP summarization information due to a failure.

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The Guard applies a naming convention to automatic packet-dump capture files that provides information about when the Guard recorded the traffic and how it handled the traffic. Table 11-1 describes the sections of the automatic packet-dump capture filename.

Table 11-1 Sections of the Automatic Packet-Dump Capture Filename 

Section	Description
Function/Zone Name	Zone function that the Guard was performing at the time of the packet-dump capture and the zone name. The zone functions are as follows: •protect—The Guard recorded the traffic during zone protection. •learn—The Guard recorded the traffic during the zone learning process or the protect and learning process.
Capture start time	Time that the Guard started recording the traffic.
Capture end time	(Optional) Time that the Guard finished recording the traffic. If the Guard is currently recording the traffic to the file, the end time is not displayed.
Dispatch	Method that the Guard used to handle the traffic. This method can be one of the following: •forwarded—The Guard identified traffic as legitimate and forwarded it to the zone. •dropped—The Guard identified traffic as malicious and dropped it. •replied—The Guard sent replies to the initiating client as part of the anti-spoofing or anti-zombie functions in order to verify whether the packets are part of authentic traffic or part of an attack.

When you enable the learning process or the protect and learning function, the Guard saves all of the packet-dump capture files that it creates. When you enable zone protection, the Guard saves one set of past packet-dump capture files only. To save all packet-dump capture files when zone protection is enabled, configure the Guard to automatically export the packet-dump capture files that it creates to a network server.

When you activate zone protection or activate the Guard to automatically record network traffic, the Guard erases all previous packet-dump capture files that it recorded during the protection process and creates new ones.

To enable the automatic packet-dump feature, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Configuration > General. The General screen appears, displaying the current zone configuration.

Step 3 Click Config. The Config screen appears.

Step 4 From the Packet-Dump Parameters area of the Zone form, click On.

Step 5 Enter the maximum amount of disk space to be used for the packet-dump captures. The disk space is defined in megabytes (MB).

Step 6 Click OK to save the automatic packet-dump setting. The Guard begins recording all the zone traffic.

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Disabling Automatic Packet-Dump Capture

You can disable the automatic packet-dump feature to stop the Guard from recording the zone traffic.

To disable the automatic packet-dump feature, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Configuration > General. The General screen appears, displaying the current zone configuration.

Step 3 Click Config. The Config screen appears.

Step 4 From the Packet-Dump Parameters area of the Zone form, click Off.

Step 5 Click OK to disable the automatic packet-dump. The Guard stops recording the zone traffic.

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Activating Manual Packet-Dump Captures

You can manually activate the Guard to record zone traffic and create a capture file, enabling you to capture traffic during a specific period of time. You can also specify the types of traffic that the Guard records as follows:

•Forwarded: Legitimate traffic that the Guard forwarded to the zone.

•Dropped: Malicious traffic that the Guard dropped.

•Replied: Traffic that the Guard anti-spoofing and anti-zombie functions send back to the source in a verification attempt.

•All: Forwarded, dropped, and replied traffic.

Within the forwarded, dropped, and replied types of packet-dump capture files, the Guard provides an IP summarization, which is a summary of the most frequently detected source IP addresses (according to the volume of traffic). The Guard does not provide an IP summarization for capture files containing all traffic types.

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Note The IP summarization process is resource consuming. When resources become low, the Guard suspends the process and issues a log message that appears in the zone log. The capture xml file will contain a status attribute stating that the capture file has no IP summarization information due to a failure.

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The Guard stops recording traffic and saves the manual packet-dump capture to a file when the specified number of packets have been recorded or when either the learning process or zone protection have ended.

The Guard allocates by default, 5 GB of disk space for manual packet-dump capture files of all zones. It can save up to 50 GB of manual and automatic packet-dump capture files of all zones. To free disk space for additional packet-dump capture files, delete any packet-dump capture files that you no longer need (see the "Deleting Packet-Dump Capture Files" section).

You can activate only one manual packet-dump capture at a time for a zone, but you can activate the manual packet-dump capture and the automatic packet-dump capture simultaneously. The Guard can record manual packet-dump captures for up to 10 zones simultaneously.

This section contains the following topics:

•Starting a Manual Packet-Dump Capture

•Stopping a Manual Packet-Dump Capture

Starting a Manual Packet-Dump Capture

The zone must be active (learning zone traffic or protecting the zone) before you can start a manual packet-dump capture.

To start a manual packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Start Packet-Dump. The Start Packet-Dump screen appears.

Step 3 Configure the parameters of the packet-dump capture.

Table 11-2 describes the parameters listed in the Start Packet-Dump form.

Table 11-2 Start Packet-Dump Form Parameters 

Parameter	Description
Capture name	Name for the packet-dump capture file. Enter an alphanumeric string from 1 to 63 characters. The string can contain underscores but cannot contain spaces.
Packet-Dump filter	(Optional) Filter that you apply to specify the traffic to record. The Guard captures only traffic that complies with the filter expression. The expression syntax is identical to the syntax of the flex-content filter expression (see the "Understanding the Flex-Content Expression Syntax" section in Chapter 5, "Configuring Zone Filters").
Dispatch value	Zone traffic that the Guard captures. Choose one of the following traffic types from the drop-down list: •all—Captures all traffic. •dropped—Captures only traffic that the Guard dropped. •forwarded—Captures only legitimate traffic that the Guard forwards on to the zone. •replied—Captures only the traffic that the Guard anti-spoofing and anti-zombie features send back to the source in a verification attempt.
Sample rate	Sample rate in packets per second. Enter a value from 1 to 10000. The Guard supports a maximum accumulated packet-dump capture rate of 10000 packets per second for all concurrent manual captures. A packet-dump capture configured with a high Sample Rate value consumes Guard resources. We recommend that you use high-rate values cautiously.
Number of packets	Number of packets to record. When the Guard records the number or packets that you specify, it stops the manual packet-dump capture and saves the information in the capture buffer to a file. Enter an integer from 1 to 5000.

Step 4 Click OK to start the manual packet-dump capture.

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Stopping a Manual Packet-Dump Capture

The Guard stops a manual packet-dump capture when it records the number of packets that you specified when you activated the capture. However, you can stop a manual packet-dump capture before the Guard records the specified number of packets.

To stop a manual packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Stop Packet-Dump. The Guard stops the manual packet-dump capture.

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Viewing Packet-Dump Captures

This section describes how to view a list of packet-dump capture files, view the content of a single packet-dump capture file, and how to compare the results of two packet-dump captures.

This section contains the following topics:

•Viewing the Packet-Dump Capture List

•Viewing the Packet-Dump Capture Details

•Changing the Packet-Dump Capture Details Screen View

•Comparing Two Packet-Dump Captures

Viewing the Packet-Dump Capture List

To view the list of packet-dump capture files, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-Dump List screen appears.

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Table 11-3 describes the fields of the packet-dump list.

Table 11-3 Packet-Dump List 

Field	Description
Name	Name of the packet-dump capture file.
Start Time	Date and time that the packet-dump capture began.
Stop Time	Date and time that the packet-dump capture ended.
Type	Type of the packet-dump capture, which can be automatic or manual.
Size	Size of the file generated by the packet-dump capture.
Packet Dump Filter	User-defined filter that the Guard used when recording traffic. The filter is in TCPDump format. The expression syntax is identical to the syntax of the flex-content filter expression (see the "Understanding the Flex-Content Expression Syntax" section in Chapter 5, "Configuring Zone Filters").
Dispatch	Traffic type that the Guard recorded. The traffic type can be one of the following: •All—All traffic. •Dropped—Traffic that the Guard dropped. •Forwarded—Legitimate traffic that the Guard forwards on to the zone. •Replied—Traffic that the Guard anti-spoofing and anti-zombie functions sent back to the source in a verification attempt.

Table 11-4 describes the function buttons of the Packet-Dump List screen.

Table 11-4 Packet-Dump List Function Buttons 

Button	Description
Stop/Start	Controls the manual packet-dump operation. This button toggles between Stop and Start depending on the current operating status of the manual packet-dump feature: •Start—Begins a manual packet-dump capture. This button displays only when no manual packet-dump capture is currently running. •Stop—Ends the current manual packet-dump capture. This button displays only when a manual packet-dump capture is currently running.
View	Displays detailed information of one or two packet-dump capture files (see the "Viewing the Packet-Dump Capture Details" and "Comparing Two Packet-Dump Captures" sections).
Rename	Changes the name of a packet-dump capture file (see the "Renaming a Manual Packet-Dump Capture File" section).
Copy	Copies a packet-dump capture file (see the "Copying a Packet-Dump Capture File" section).
Export/Import	Exports or imports a packet-dump capture file (see the "Exporting Packet-Dump Capture Files" and "Importing Packet-Dump Capture Files" sections).
Delete	Deletes a packet-dump capture file (see the "Deleting Packet-Dump Capture Files" section).

Viewing the Packet-Dump Capture Details

To view the details of a packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-Dump List screen appears.

Step 3 Check the check box next to the packet-dump capture that you want to view, and then click View.

The Packet-Dump capture analysis screen appears. For information about applying a screen filter to the information displayed, see the "Changing the Packet-Dump Capture Details Screen View" section.

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Table 11-5 describes the information that the Guard displays in the Capture and View parameter areas of the Packet-Dump Capture Analysis screen.

Table 11-5 Packet-Dump Capture and View Parameters 

Screen Area	Parameter	Description
Capture parameters	Name	Name of the capture file.
	Start time	Time that the capture started.
	End time	Time that the capture ended.
	Packets	Number of packets that the capture file contains.
	Packet Dump filter	User-defined filter that the Guard used when recording traffic. The filter is in TCPDump format. The expression rules are identical to the Flex-content filter expression rules.
	Dispatch	Traffic type that the Guard recorded: •All—All traffic. •Dropped—Traffic that the Guard dropped. •Forwarded—Legitimate traffic that the Guard forwarded on to the zone. •Replied—Traffic that the Guard anti-spoofing and anti-zombie functions sent back to the source in a verification attempt.
View Parameters	Query	Data profile that the Guard uses to display the capture information: •Top 20: SrcIP / DstIP / SrcPort / DstPort / Protocol •Distribution: SrcIP / DstIP / SrcPort / DstPort / SrcReservedPorts / DstReservedPorts / Protocol / TTL / Length •Packets list See Table 11-7 for details about the information that the Guard displays for each of the query types.
	Display filter	Filter that the Guard uses when displaying the packet-dump capture file. The Guard displays only the portion of the packet-dump capture file that matches the filter criteria. The expression rules are identical to the flex-content filter expression rules.

The IP Summarization table, located under the View Parameters section, displays information on the most frequently detected IP addresses recorded in the packet-dump capture. Table 11-6 describes the fields that display in the IP Summarization table.

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Note If you display two packet-dump captures to do a comparison of the two captures (see the "Comparing Two Packet-Dump Captures" section), the IP summarization table does not display.

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Table 11-6 Field Descriptions for the IP Summarization Table

Field	Description
Subnet	Most frequently detected IP addresses of the recorded packet type. For forwarded and dropped packet types, the IP addresses listed are the packet source IP addresses. For replied packet types, the IP addresses are the packet destination IP addresses.
Subnet Mask	Subnet mask of the recorded packet type (forwarded, dropped, or replied).
Weight (%)	Percentage of samples recorded by the Guard that came from the subnet IP address out of the total number of recorded samples.
Unique Addresses	Number of unique addresses belonging to the subnet.

Table 11-7 describes the capture information that the Guard displays, which varies based on the type of query that you select (see the "Changing the Packet-Dump Capture Details Screen View" section).

Table 11-7 Capture Parameters Table and Graph Details 

Query Type	Parameter	Description
Top 20/Criteria The Criteria can be one of the following: •SrcIP •DstIP •SrcPort •DstPort •Protocol	#	Sequential number that the Guard assigned to each incident that it recorded during the packet-dump capture.
	Key	IP address, port number, or protocol number, which varies based on the query type that you chose.
	Packets	Number of packets in the packet-dump capture.
	%	Percentage of packets in the packet-dump capture that fit the criteria.
Distribution/Criteria The Criteria can be one of the following: •SrcIP •DstIP •SrcPort •DstPort •SrcReservedPorts •DstReservedPorts •Protocol •TTL •Length	x-axis	Units of the distribution attribute that you chose, such as the IP address, the port number, or the protocol number.
	y-axis	Number of packets.
Packets List	#	Sequential number that the Guard assigned to each incident that it recorded during the packet-dump capture.
	Time	Time that the packet-dump was captured.
	ScrIp	Source IP address of the packets.
	ScrPort	Source port of the packets.
	DstIp	Destination IP address of the packets.
	DstPort	Destination port of the packets.
	Protocol	Protocol number of the packets.
	Info	Additional information on the packets.

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Note To sort the information in a Top 20 table and a Packets List table based on the column information, click on the table column header.

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The Packet-Dump capture analysis screen contains the following function buttons:

•Change View—Changes the view parameters (see the "Changing the Packet-Dump Capture Details Screen View" section).

•Save—Saves a copy of the packet-dump capture to a different filename (see the "Copying a Packet-Dump Capture File" section).

•Extract Signatures—Extracts the traffic signature from the packet-dump capture (see the "Extracting an Attack Signature from a Packet-Dump Capture" section).

Changing the Packet-Dump Capture Details Screen View

To change the view of the Packet-Dump Capture details screen, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-Dump List screen appears.

Step 3 Click Change View. The Change Packet-Dump View Parameters window opens.

Step 4 Configure the viewing parameters of the packet-dump capture. Table 11-8 describes the parameters of the Change Packet-Dump View Parameters form.

Table 11-8 Change Packet-Dump View Parameters 

Parameter	Description
Query	Data profile to display. Choose one of the following profiles from the Query drop-down list: •TOP 20: SrcIP / DstIP / SrcPort / DstPort / Protocol— Groups the packets based on the criteria that you chose and then displays 20 groups with the highest values. For example, if you choose the display criteria to be Src IP, the Guard groups the packets based on the source IP address and then displays information about the 20 source IP addresses that appeared the highest number of times. The information displays in a table format. •Distribution: SrcIP / DstIP / SrcPort / DstPort / SrcReservedPorts / DstReservedPorts / Protocol / TTL / Length—Displays a graph indicating how the packets are distributed across the criteria that you defined. •Packet View—Displays packet details, such as source and destination IP addresses, and source and destination ports. The information displays in a table format. The profile determines the format of the display (table or graph).
Display filter	(Optional) User-defined filter that specifies which packets to display. The Guard displays only the portion of the packet-dump capture file that matches the filter criteria. The expression rules are identical to the flex-content filter TCPDump expression rules (see the "Understanding the Flex-Content Expression Syntax" section in Chapter 5, "Configuring Zone Filters").
Display Pattern	(Optional) Regular expression data pattern to match with the packet content. The Guard displays only the portion of the packet-dump capture file that matches the pattern criteria. The pattern rules are identical to the flex-content pattern rules (see the "Understanding the Flex-Content Filter Pattern Syntax" section in Chapter 5, "Configuring Zone Filters"). Enter the display pattern to use. You can also use an attack signature as the Display Pattern. See the "Using an Attack Signature as a Display Pattern for Displaying Packet-Dump Captures" section for more information.
Start Offset	(Optional) Offset, in bytes, from the beginning of the packet payload where the pattern matching begins. The default is 0 (the start of the payload). The Start Offset parameter applies only if you enter a pattern in the Display Pattern field. Enter the start offset to use.
End Offset	(Optional) Offset, in bytes, from the beginning of the packet payload where the pattern-matching ends. The default is the packet length (the end of the payload). The End Offset parameter applies only if you enter a pattern in the Display Pattern field. Enter the end offset to use.

Step 5 Click OK to change the packet-dump display. The Guard updates the packet-dump capture details screen based on the view parameters that you chose.

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Comparing Two Packet-Dump Captures

To compare the details of two packet-dump captures, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-Dump List screen appears.

Step 3 Check the check box next to the packet-dump capture that you want to view as the base capture.

Step 4 Check the check box next to the packet-dump capture that you want to view as the reference capture.

Step 5 Click View. The Packet-Dump capture analysis screen appears, displaying the details of the base and reference packet-dump captures.

Step 6 (Optional) Click Swap Base and Reference to switch the two packet captures, making the base capture the reference capture and the reference capture the base capture. Use this function when extracting a signature (the Guard extracts the signature from the base capture). For information about extracting a signature, see the "Extracting and Using Signatures from Packet-Dump Captures" section.

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For a description of the information that the Guard displays in the Packet-Dump capture analysis screen, see the "Viewing the Packet-Dump Capture Details" section.

Managing Packet-Dump Capture Files

This section contains the following topics:

•Renaming a Manual Packet-Dump Capture File

•Copying a Packet-Dump Capture File

•Exporting Packet-Dump Capture Files

•Importing Packet-Dump Capture Files

•Deleting Packet-Dump Capture Files

Renaming a Manual Packet-Dump Capture File

You can rename a manual packet-dump capture file, but you cannot rename an automatic packet-dump capture file. To change the name of an automatic packet-dump capture file, you must copy the file (see the "Copying a Packet-Dump Capture File" section).

To rename a manual packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-Dump List screen appears.

Step 3 Check the check box next to the packet-dump capture that you want to rename, and then click Rename. The Rename window opens.

Step 4 In the New name field, enter a new name for the packet-dump capture file. The name is an alphanumeric string from 1 to 63 characters and can contain underscores and dashes but cannot contain spaces.

Step 5 Click OK to save the packet-dump capture using the new name.

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Copying a Packet-Dump Capture File

You can copy a packet-dump capture file (or a portion of a file) under a new name. Because the Guard overwrites existing automatic packet-dump capture files with new ones, the copy option enables you to save an automatic packet-dump capture file for use at a later time. When you copy an automatic packet-dump capture file or a manual packet-dump capture file, the Guard saves them as manual files and does not delete the original packet-dump capture file. You must manually delete them if you need to free disk space (see the "Deleting Packet-Dump Capture Files" section).

To copy a packet-dump capture file, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-dump List screen appears.

Step 3 Check the check box next to the packet-dump capture that you want to copy, and then click Copy. The Packet-Dump capture analysis screen appears.

Step 4 In the New name field, enter a new name for the packet-dump capture file. The name is an alphanumeric string from 1 to 63 characters and can contain underscores and dashes but cannot contain spaces.

Step 5 (Optional) Define the filter that the Guard uses to copy the packet-dump capture file. The Guard copies only the portion of the packet-dump capture file that matches the filter criteria. The expression rules are identical to the flex-content filter expression rules (see the "Understanding the Flex-Content Expression Syntax" section in Chapter 5, "Configuring Zone Filters").

Step 6 Click OK to save the packet-dump capture using the new name.

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You can also copy a file by displaying the packet-dump capture details (see the "Viewing the Packet-Dump Capture Details" section) and then click Save. The Guard saves the portion of the files that is displayed. If you configure a filter that the Guard uses to display the packet-dump capture file, the Guard uses the same filter to save the portion of the packet-dump capture file that matches the filter criteria.

Exporting Packet-Dump Capture Files

You can manually export packet-dump capture files to a network server that uses FTP, Secure File Transfer Protocol (SFTP), or Secure Copy Protocol (SCP) to transfer files. You can export a single packet-dump capture file or all packet-dump capture files of a specific zone. The Guard exports the packet-dump capture files in a PCAP format, which is compressed and encoded by the gzip (GNU zip) program with an accompanying file in an XML format that describes the recorded data. See the Capture.xsd file that accompanies the version for a description of the XML schema.

You can download the .xsd files that accompany the version from the Software Center at http://www.cisco.com/public/sw-center/.

To export a packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-dump List screen appears.

Step 3 Check the check box next to the packet-dump capture files that you want to export, and then click Export. The Export File Server Parameters window opens.

To choose all of the packet-dump captures, check the check box in the table header.

Step 4 From the Select File Server Parameters form, choose the network server to use:

•Use automatic export file server definitions—Exports the packet-dump capture files to the network servers that you defined in the Guard configuration by using the CLI export packet-dump command.

•Use the following server definition—Exports the packet-dump capture files to the network server that you define. Enter the following network server information:

–Transfer method—Transfer protocol to use. The transfer method can be one of the following:

FTP—Specifies FTP.

SFTP—Specifies SFTP.

SCP—Specifies SCP.

Because SFTP and SCP rely on Secure Shell (SSH) for their secure transport, if you do not configure the key that the Guard uses for the secure communication before you export attack reports to an SFTP or SCP server, the Guard prompts you for the password. You must use the Guard CLI to configure the key for SFTP and SCP.

–Address—IP address of the network server.

–Path—Complete pathname where the Guard saves the packet-dump capture files. If you do not specify a path, the network server saves the packet-dump capture files in your home directory.

–Username—Network server login name. The username argument is optional when you define an FTP server. When you do not insert a login name, the FTP server assumes an anonymous login and does not prompt you for a password.

–Password—(Optional) Password for the remote FTP server. If you enter a username but do not enter a password, the Guard prompts you for the password.

Step 5 Click OK to export the packet-dump capture files to the network server.

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Importing Packet-Dump Capture Files

You can import packet-dump capture files from a network server to the Guard to analyze past events or to compare current network traffic patterns with traffic patterns that the Guard recorded previously under normal traffic conditions. The Guard imports a packet-dump capture file in both XML and PCAP formats.

To import a packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-dump List screen appears.

Step 3 Click Import. The Import FTP Server Parameters window opens.

Step 4 In the File Name field, enter the complete path and filename, excluding the file extension, of the file to import. If you do not specify a path, the server copies the file from your home directory.

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Note Do not specify the file extension because it will cause the import process to fail.

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Step 5 From the Select File Server Parameters form, choose the network server to use:

•Use automatic export file server definitions—Imports the packet-dump capture files from the network servers that you defined in the Guard configuration by using the CLI export packet-dump command.

•Use the following server definition—Imports the packet-dump capture files from the network server that you define. Enter the following network server information:

–Transfer method—Transfer protocol to use. The transfer method can be one of the following:

FTP—Specifies FTP.

SFTP—Specifies SFTP.

SCP—Specifies SCP.

Because SFTP and SCP rely on SSH for their secure transport, if you do not configure the key that the Guard uses for the secure communication before you export attack reports to an SFTP or SCP server, the Guard prompts you for the password. You can only configure the key for SFTP and SCP using the Guard CLI.

–Address—IP address of the network server.

–Path—Complete pathname from where the Guard imports the packet-dump capture files. If you do not specify a path, the network server copies the packet-dump capture file from your home directory.

–Username—Network server login name. The username argument is optional when you define an FTP server. When you do not insert a login name, the FTP server assumes an anonymous login and does not prompt you for a password.

–Password—(Optional) Password for the remote FTP server. If you enter a username but do not enter a password, the Guard prompts you for the password.

Step 6 Click OK to import the packet-dump capture file from the network server.

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Deleting Packet-Dump Capture Files

The Guard allocates by default, 5 GB of disk space for the manual packet-dump capture files of all zones. It can save up to 50 GB of manual and automatic packet-dump capture files of all zones. To free disk space for additional packet-dump capture files, delete the old ones.

You can save a maximum of 10 packet-dump capture files on the Guard. You must delete old manual packet-dump capture files to allow space for new files.

To delete a packet-dump capture, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-dump List screen appears.

Step 3 Check the check box next to the packet-dump captures that you want to delete, and then click Delete. The Guard deletes the packet-dump capture files.

To choose all of the packet-dump captures, choose the check box in the table header.

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Extracting and Using Signatures from Packet-Dump Captures

An attack signature describes the common pattern that appears in the payload of attack packets. You can activate the Guard to generate the signature of anomalous traffic and then use this information to quickly identify future attacks of the same type. This feature allows you to detect new Distributed Denial of Service (DDoS) attacks and Internet worms, even before signatures are published (for example, from antivirus software companies or mailing lists).

The Guard generates the attack signature using the flex-content filter pattern expression syntax. You can use this signature in the flex-content filter pattern to filter out anomalous traffic. See the "Understanding the Flex-Content Filter Pattern Syntax" section in Chapter 5, "Configuring Zone Filters."

You can specify an additional packet-dump capture file that the Guard recorded during normal traffic conditions as a reference. If you specify a reference packet-dump capture file, the Guard generates the signature from the anomalous traffic and specifies the percentage of time that the signature is present in traffic that was recorded during normal traffic conditions.If the attack signature appears in a high percentage of the normal traffic recording, the signature may not be an accurate representation of the attack pattern.

This section contains the following topics:

•Extracting an Attack Signature from a Packet-Dump Capture

•Adding an Attack Signature to a Flex-Content Filter

•Using an Attack Signature as a Display Pattern for Displaying Packet-Dump Captures

Extracting an Attack Signature from a Packet-Dump Capture

To extract an attack signature from a packet-dump capture file, perform the following steps:

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Step 1 From the navigation pane, choose a zone. The zone main menu appears.

Step 2 From the zone main menu, choose Diagnostics > Packet-Dump > Packet-Dump List. The Packet-dump List screen appears.

Step 3 Check the check box next to the packet-dump capture from which to extract the signature.

Step 4 (Optional) Check the check box next to the packet-dump capture that you want to use as a reference. The reference should be a capture file of traffic that was recorded during normal traffic conditions.

Step 5 Click View. The Packet-Dump Capture Analysis screen appears.

Step 6 (Optional) Click Swap Base and Reference to switch the two packet captures, making the base capture the reference capture, and the reference capture the base capture. The Guard extracts the signature from the base capture.

Step 7 Click Extract Signatures. The Guard extracts the signatures from the base packet-dump capture and opens the Packet-Dump Signature Extraction window.

Table 11-9 describes the signature information that the Guard displays in the Packet-Dump Signature Extraction window.

Table 11-9 Packet-Dump Signature Extraction Parameters 

Parameter	Description
Capture name	Name of the packet-dump capture from which the Guard extracted the signature.
Pattern	List of the patterns (in an abbreviated format) that the Guard extracted from the packet-dump capture. Move the mouse over the pattern to display the complete pattern.
Start offset	Offset, in bytes, from the beginning of the packet payload, where the pattern matching begins. The default is 0, which is the start of the payload.
End offset	Offset, in bytes, from the beginning of the packet payload, where the pattern matching ends. The default is the packet length, which is the end of the payload.
% Reference	Percentage of time that the signature is present in the reference capture file.

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To add one of the signatures that the Guard displays to a flex-content filter, see the "Adding an Attack Signature to a Flex-Content Filter" section.

Adding an Attack Signature to a Flex-Content Filter

The Guard allows you to create a flex-content filter using a signature that it extracts from the packet-dump capture. You can then use the flex-content filter to block the zone traffic that matches the attack signature.

To add an attack signature to a flex-content filter, perform the following steps:

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Step 1 Extract the signatures from a packet-dump capture. See the "Extracting an Attack Signature from a Packet-Dump Capture" for more information.

Step 2 From the Packet-Dump Signature Extraction window, choose the signature that you want to use in the flex-content filter, and then click Insert Content Filter. The Flex-Content Filters > Add Filter - Step 2 screen appears.

Step 3 Configure the flex-content filter parameters. Table 11-10 describes the filter parameters listed in the Flex-Content Filter form.

Table 11-10 Flex-Content Filter Parameters 

Parameter	Description
Description	Text describing the flex-content filter.
Protocol	Processes traffic using a specific protocol. Enter a protocol number from 0 to 255. To specify any protocol type, enter an asterisk (*). Refer to the Internet Assigned Numbers Authority (IANA) website for a list of valid protocol numbers: http://www.iana.org/assignments/protocol-numbers
Dst Port	Processes traffic flowing to a specific destination port. Enter a destination port number from 0 to 65535. To specify any destination port, enter an asterisk (*). Refer to the Internet Assigned Numbers Authority (IANA) website for a list of valid port numbers: http://www.iana.org/assignments/port-numbers
Expression	Filters traffic based on the specified expression (see the "Understanding the Flex-Content Expression Syntax" section in Chapter 5, "Configuring Zone Filters"). Enter the expression to use.
Pattern	Specifies the regular expression data pattern that is to be matched with the packet content (see the "Understanding the Flex-Content Filter Pattern Syntax" section in Chapter 5, "Configuring Zone Filters"). Enter the data pattern to use.
Match Case	Specifies whether the pattern expression that the filter matches is case sensitive or not case sensitive. Check the check box to define the data pattern expression as case sensitive.
Start Offset	Specifies the offset (in bytes) from the beginning of the packet content where the pattern matching begins. The default is 0, which is the start of the payload. The start offset applies to the pattern field. Enter an integer from 0 to 2047.
End Offset	Specifies the offset (in bytes) from the beginning of the packet content where the pattern matching ends. The default is the packet length, which is the end of the payload. The end offset applies to the pattern field. Enter an integer from 0 to 2047.
Action	Specifies the action that the flex-content filter performs on the traffic. Choose one of the following actions from the Action drop-down list: •count—Counts the traffic flow packets that match the filter. •drop—Drops the traffic flow packets that match the filter.
State	Specifies the operating state of the flex-content filter. Choose one of the following operating states from the State drop-down list: •enable—The Guard applies the filter to the traffic flow and executes the configured action on the flow that matches the filter. •disable—The Guard does not apply the filter to the traffic flow.

Step 4 Click OK to save the new flex-content filter.

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Using an Attack Signature as a Display Pattern for Displaying Packet-Dump Captures

The Guard allows you to filter the packet-dump capture display using a signature that it extracts from the packet-dump capture.

To use an attack signature as a display pattern for displaying packet-dump captures, perform the following steps:

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Step 1 Extract the signatures from a packet-dump capture. See the "Extracting an Attack Signature from a Packet-Dump Capture" for more information.

Step 2 From the Packet-Dump Signature Extraction window, choose the signature that you want to use as the display pattern, and then click Use as View Filter. The Packet-Dump Capture analysis screen appears.

Table 11-11 describes the information that the Guard displays in the Capture and View parameter areas of the Packet-Dump capture analysis screen.

Table 11-11 Packet-Dump Capture and View Parameters 

Screen Area	Parameter	Description
Capture parameters	Name	Name of the capture file.
	Start time	Time that the capture started.
	End time	Time that the capture ended.
	Packets	Number of packets that the capture file contains.
	Packet Dump filter	User-defined filter that the Guard used when recording traffic. The filter is in TCPDump format. The expression rules are identical to the flex-content filter expression rules.
	Dispatch	Traffic type that the Guard recorded: •All—All traffic. •Dropped—Traffic that the Guard dropped. •Forwarded—Legitimate traffic that the Guard forwarded on to the zone. •Replied—Traffic that the Guard anti-spoofing and anti-zombie functions sent back to the source in a verification attempt.
View Parameters	Query	Data profile that the Guard uses to display the capture information: •Top 20: SrcIP / DstIP / SrcPort / DstPort / Protocol •Distribution: SrcIP / DstIP / SrcPort / DstPort / SrcReservedPorts / DstReservedPorts / Protocol / TTL / Length •Packets list See Table 11-7 for details about the information that the Guard displays for each of the query types.
	Display filter	Filter that the Guard uses when displaying the packet-dump capture file. The Guard displays only the portion of the packet-dump capture file that matches the filter criteria. The expression rules are identical to the flex-content filter expression rules.

Table 11-12 describes the capture information that the Guard displays, which varies based on the type of query that you choose (see the "Changing the Packet-Dump Capture Details Screen View" section).

Table 11-12 Capture Parameters Table and Graph Details 

Query Type	Parameter	Description
Top 20/Criteria The Criteria can be one of the following: •SrcIP •DstIP •SrcPort •DstPort •Protocol	#	Sequential number that the Guard assigned to each incident that it recorded during the packet-dump capture.
	Key	IP address, port number, or protocol number, which varies based on the query type that you chose.
	Packets	Number of packets in the packet-dump capture.
	%	Percentage of packets in the packet-dump capture that fit the criteria.
Distribution/Criteria The Criteria can be one of the following: •SrcIP •DstIP •SrcPort •DstPort •SrcReservedPorts •DstReservedPorts •Protocol •TTL •Length	x-axis	Units of the distribution attribute that you select, such as IP address, port number, or protocol number.
	y-axis	Number of packets.
Packets List	#	Sequential number that the Guard assigned to each incident that it recorded during the packet-dump capture.
	Time	Time that the packet-dump was captured.
	ScrIp	Source IP address of the packets.
	ScrPort	Source port of the packets.
	DstIp	Destination IP address of the packets.
	DstPort	Destination port of the packets.
	Protocol	Protocol number of the packets.
	Info	Additional information on the packets.

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Note To sort the information in a Top 20 table and a Packets List table based on the column information, click on the table column header.

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