Cisco Intrusion Prevention System Sensor CLI Configuration Guide for IPS 7.1
Configuring Global Correlation
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Table of Contents

Configuring Global Correlation

Global Correlation Notes and Caveats

Understanding Global Correlation

Participating in the SensorBase Network

Understanding Reputation

Understanding Network Participation

Understanding Efficacy

Understanding Reputation and Risk Rating

Global Correlation Features and Goals

Global Correlation Requirements

Understanding Global Correlation Sensor Health Metrics

Configuring Global Correlation Inspection and Reputation Filtering

Understanding Global Correlation Inspection and Reputation Filtering

Configuring Global Correlation Inspection and Reputation Filtering

Configuring Network Participation

Troubleshooting Global Correlation

Disabling Global Correlation

Displaying Global Correlation Statistics

Global Correlation Notes and Caveats

The following notes and caveats apply to configuring global correlation:

  • The global correlation features are supported in IPS 7.0 and later.
  • As with signature updates, when the sensor applies a global correlation update, it may trigger bypass. Whether or not bypass is triggered depends on the traffic load of the sensor and the size of the signature/global correlation update. If bypass mode is turned off, an inline sensor stops passing traffic while the update is being applied.
  • Network participation requires a network connection to the Internet.
  • Valid license—You must have a valid sensor license for global correlation features to function. You can still configure and display statistics for the global correlation features, but the global correlation databases are cleared and no updates are attempted. Once you install a valid license, the global correlation features are reactivated.
  • Global correlation inspection and the reputation filtering deny features do not support IPv6 addresses. For global correlation inspection, the sensor does not receive or process reputation data for IPv6 addresses. The risk rating for IPv6 addresses is not modified for global correlation inspection. Similarly, network participation does not include event data for attacks from IPv6 addresses. And finally, IPv6 addresses do not appear in the deny list.
  • The sensor must operate in inline mode so that the global correlation features can increase efficacy by being able to use the inline deny actions.
  • For global correlation to function, you must have either a DNS server or an HTTP proxy server configured at all times.

Understanding Global Correlation

You can configure global correlation so that your sensors are aware of network devices with a reputation for malicious activity, and can take action against them. Participating IPS devices in a centralized Cisco threat database, the SensorBase Network, receive and absorb global correlation updates. The reputation information contained in the global correlation updates is factored in to the analysis of network traffic, which increases IPS efficacy, since traffic is denied or allowed based on the reputation of the source IP address. The participating IPS devices send data back to the Cisco SensorBase Network, which results in a feedback loop that keeps the updates current and global.

You can configure the sensor to participate in the global correlation updates and/or in sending telemetry data or you can turn both services off. You can view reputation scores in events and see the reputation score of the attacker. You can also view statistics from the reputation filter.

Participating in the SensorBase Network

The Cisco IPS contains a security capability, Cisco Global Correlation, which uses the immense security intelligence that we have amassed over the years. At regular intervals, the Cisco IPS receives threat updates from the Cisco SensorBase Network, which contain detailed information about known threats on the Internet, including serial attackers, Botnet harvesters, Malware outbreaks, and dark nets. The IPS uses this information to filter out the worst attackers before they have a chance to attack critical assets. It then incorporates the global threat data in to its system to detect and prevent malicious activity even earlier.

If you agree to participate in the SensorBase Network, Cisco will collect aggregated statistics about traffic sent to your IPS. This includes summary data on the Cisco IPS network traffic properties and how this traffic was handled by the Cisco appliances. We do not collect the data content of traffic or other confidential business or personal information. All data is aggregated and sent by secure HTTP to the Cisco SensorBase Network servers in periodic intervals. All data shared with Cisco will be anonymous and treated as strictly confidential.

Table 10-1 shows how we use the data.

 

Table 10-1 Cisco Network Participation Data Use

Participation Level
Type of Data
Purpose

Partial

Protocol attributes
(TCP maximum segment size and options string, for example)

Tracks potential threats and helps us to understand threat exposure.

Attack type
(signature fired and risk rating, for example)

Used to understand current attacks and attack severity.

Connecting IP address and port

Identifies attack source.

Summary IPS performance
(CPU utilization, memory usage, inline vs. promiscuous, for example)

Tracks product efficacy.

Full

Victim IP address and port

Detects threat behavioral patterns.

When you enable Partial or Full Network Participation, the Network Participation Disclaimer appears. You must enter yes to participate. If you do not have a license installed, you receive a warning telling you that global correlation inspection and reputation filtering are disabled until the sensor is licensed. You can obtain a license at http://www.cisco.com/go/license .

For More Information

For information on how to obtain and install a sensor license, see Installing the License Key.

Understanding Reputation

Similar to human social interaction, reputation is an opinion toward a device on the Internet. It enables the installed base of IPS sensors in the field to collaborate using the existing network infrastructure. A network device with reputation is most likely either malicious or infected. You can view reputation information and statistics in the IDM, IME, or the CLI.

The IPS sensor collaborates with the global correlation servers (also known as reputation servers) to improve the efficacy of the sensor.

Figure 10-1 shows the role of the sensor and the global correlation servers.

Figure 10-1 IPS Management and Global Correlation Server Interaction

 

The global correlation servers provide information to the sensor about certain IP addresses that may identify malicious or infected hosts. The sensor uses this information to determine which actions, if any, to perform when potentially harmful traffic is received from a host with known reputation. Because the global correlation database changes rapidly, the sensor must periodically download global correlation updates from the global correlation servers.


Caution As with signature updates, when the sensor applies a global correlation update, it may trigger bypass. Whether or not bypass is triggered depends on the traffic load of the sensor and the size of the signature/global correlation update. If bypass mode is turned off, an inline sensor stops passing traffic while the update is being applied.

For More Information

For more information about viewing global correlation statistics, see Displaying Statistics.

Understanding Network Participation

Network participation lets us collect nearly real-time data from sensors around the world. Sensors installed at customer sites can send data to the SensorBase Network. These data feed in to the global correlation database to increase reputation fidelity. Communication between sensors and the SensorBase Network involves an HTTPS request and response over TCP/IP. Network participation gathers the following data:

  • Signature ID
  • Attacker IP address
  • Attacker port
  • Maximum segment size
  • Victim IP address
  • Victim port
  • Signature version
  • TCP options string
  • Reputation score
  • Risk rating
  • Data gathered from the sensor health metrics

The statistics for network participation show the hits and misses for alerts, the reputation actions, and the counters of packets that have been denied.


Note Network participation requires a network connection to the Internet.


There are three modes for network participation:

  • Off—The network participation server does not collect data, track statistics, or try to contact the Cisco SensorBase Network.
  • Partial Participation—The network participation server collects data, tracks statistics, and communicates with the SensorBase Network. Data considered to be potentially sensitive is filtered out and never sent.
  • Full Participation—The network participation server collects data, tracks statistics, and communicates with the SensorBase Network. All data collected is sent except the IP addresses that you exclude from the network participation data.

Caution As with signature updates, when the sensor applies a global correlation update, it may trigger bypass. Whether or not bypass is triggered depends on the traffic load of the sensor and the size of the signature/global correlation update. If bypass mode is turned off, an inline sensor stops passing traffic while the update is being applied.

For More Information

Understanding Efficacy

Obtaining data from participating IPS clients and using that in conjunction with the existing corpus of threat knowledge improves the efficacy of the IPS. We measure efficacy based on the following:

  • False positives as a percentage of actionable events
  • False negatives as a percentage of threats that do not result in actionable events
  • Actionable events as a percentage of all events

The IPS signature team uses the data to improve signature fidelity and the IPS engineering team uses the data to better understand the various types of sensor deployment.

For More Information

For more information about reputation and risk rating, see Understanding Reputation and Risk Rating.

Understanding Reputation and Risk Rating

Risk rating is the concept of the probability that a network event is malicious. You assign a numerical quantification of the risk associated with a particular event on the network. By default, an alert with an extreme risk rating shuts down traffic. Reputation indicates the probability that a particular attacker IP address will initiate malicious behavior based on its known past activity. A certain score is computed for this reputation by the Alarm Channel and added to risk rating, thus improving the efficacy of the IPS. When the attacker has a bad reputation score, an incremental risk is added to the risk rating to make it more aggressive.

The Alarm Channel handles signature events from the data path. The alert processing units have multiple aggregation techniques, action overrides, action filters, attacker reputation, and per-action custom handling methods. We use the large reputation data from the reputation participation client to score attackers in the Alarm Channel and then use this score to influence the risk rating and actions of the alert.

For More Information

Global Correlation Features and Goals

There are three main features of global correlation:

  • Global Correlation Inspection—We use the global correlation reputation knowledge of attackers to influence alert handling and deny actions when attackers with a bad score are seen on the sensor.
  • Reputation Filtering—Applies automatic deny actions to packets from known malicious sites.
  • Network Reputation—Sensor sends alert and TCP fingerprint data to the SensorBase Network.

Global correlation has the following goals:

  • Dealing intelligently with alerts thus improving efficacy.
  • Improving protection against known malicious sites.
  • Sharing telemetry data with the SensorBase Network to improve visibility of alerts and sensor actions on a global scale.
  • Simplifying configuration settings.
  • Automatic handling of the uploads and downloads of the information.

Global Correlation Requirements

Global correlation has the following requirements:

  • Valid license—You must have a valid sensor license for global correlation features to function. You can still configure and display statistics for the global correlation features, but the global correlation databases are cleared and no updates are attempted. Once you install a valid license, the global correlation features are reactivated.
  • Network Participation disclaimer—You must agree to the disclaimer to participate.
  • External connectivity for the sensor and a DNS server—The global correlation features of Cisco IPS require the sensor to connect to the Cisco SensorBase Network. Domain name resolution is also required for these features to function. You can either configure the sensor to connect through an HTTP proxy server that has a DNS client running on it, or you can assign an Internet routeable address to the management interface of the sensor and configure the sensor to use a DNS server. In Cisco IPS the HTTP proxy and DNS servers are used only by the global correlation features.

If you are connecting through an HTTP proxy, make sure you have the following configuration:

The proxy must allow HTTP requests from the IPS systems to http://updates.ironport.com/ibrs/ on port 80.

The proxy must allow HTTPS requests from the IPS systems to update-manifests.ironport.com on port 443.

The firewall must allow access from the proxy to the internet (any destination address) on ports 80 and 443.

If you are NOT connecting through the HTTP proxy:

The firewall must allow access from each IPS to the Internet (any destination address) on ports 80 and 443.


Note The IPS does not support the use of authenticated proxies.


  • Sensors deployed in an environment with a slow command and control connection will be slow to download global correlation updates.
  • No IPv6 address support—Global correlation inspection and the reputation filtering deny features do not support IPv6 addresses. For global correlation inspection, the sensor does not receive or process reputation data for IPv6 addresses. The risk rating for IPv6 addresses is not modified for global correlation inspection. Similarly, network participation does not include event data for attacks from IPv6 addresses. And finally, IPv6 addresses do not appear in the deny list.
  • Sensor in inline mode—The sensor must operate in inline mode so that the global correlation features can increase efficacy by being able to use the inline deny actions.
  • Sensor that supports the global correlation features.
  • IPS version that supports the global correlation features.

For More Information

Understanding Global Correlation Sensor Health Metrics

For global correlation, the following metrics are added to sensor health monitoring:

  • Green indicates that the last update was successful.
  • Yellow indicates that there has not been a successful update within the past day (86,400 seconds).
  • Red indicates that there has not been a successful update within the last three days (259,200 seconds).

For network participation, the following metrics are added to sensor health monitoring:

  • Green indicates that the last connection was successful.
  • Yellow indicates that less than 6 connections failed in a row.
  • Red indicates that more than 6 connections failed in a row.

Use the health-monitor command in service submode to configure the health statistics for the sensor. Use the show health command to see the results of the health-monitor command.

Global correlation health status defaults to red and changes to green after a successful global correlation update. Successful global correlation updates require a DNS server or an HTTP proxy server. Because DNS and HTTP proxy server configuration features are beginning with IPS 7.0(1)E3, they are unconfigured after an upgrade from 6. x to 7.0(1)E3 or higher. As a result, global correlation health and overall sensor health status are red until you configure a DNS or HTTP proxy server on the sensor. If the sensor is deployed in an environment where a DNS or HTTP proxy server is not available, you can address the red global correlation health and overall sensor health status by disabling global correlation and configuring sensor health status not to include global correlation health status.

For More Information

Configuring Global Correlation Inspection and Reputation Filtering

This section describes global correlation inspection and reputation filtering, and how to configure them. It contains the following topics:

Understanding Global Correlation Inspection and Reputation Filtering

You can configure the sensor to use updates from the SensorBase Network to adjust the risk rating. The client determines which updates are available and applicable to the sensor by communicating with the global correlation update server and a file server, which is a two-phase process. In the first phase the sensor sends a client manifest to the global correlation update sever via an HTTPS POST request. The server then returns the server manifest document in the HTTPS response. In the next phase the sensor identifies the updates that are available and how to obtain them from a file server. The sensor downloads the encrypted update files via HTTP from the file server using the information in the server manifest. The integrity of these update files has been verified by comparing its MD5 hash with the hash value specified in the server manifest.

Figure 10-2 demonstrates how the global correlation update client obtains the files.

Figure 10-2 Global Correlation Update Client

 


Caution You must have a valid sensor license for global correlation features to function. You can still configure and display statistics for the global correlation features, but the global correlation databases are cleared and no updates are attempted. Once you install a valid license, the global correlation features are reactivated.

Once you configure global correlation, updates are automatic and happen at regular intervals, approximately every five minutes by default, but this interval may be modified by the global correlation server. The sensor gets a full update and then applies an incremental update periodically.

You configure an HTTP proxy or a DNS server in the service network-setting submode. If you turn on global correlation, you can choose how aggressively you want the deny actions to be enforced against malicious hosts. You can then enable reputation filtering to deny access to known malicious hosts. If you only want a report of what could have happened, you can enable test-global-correlation . This puts the sensor in audit mode, and actions the sensor would have performed are generated in the events.

Use the show health command in privileged EXEC mode to display the overall health status information of the sensor. The health status categories are rated by red and green with red being critical.


Caution As with signature updates, when the sensor applies a global correlation update, it may trigger bypass. Whether or not bypass is triggered depends on the traffic load of the sensor and the size of the signature/global correlation update. If bypass mode is turned off, an inline sensor stops passing traffic while the update is being applied.

For More Information

Configuring Global Correlation Inspection and Reputation Filtering


Caution For global correlation to function, you must have either a DNS server or an HTTP proxy server configured at all times.

The following options apply:

  • global-correlation-inspection {on | off} —Turns global correlation inspection on or off. When turned on, the sensor uses updates from the SensorBase network to adjust the risk rating. The default is on.
  • global-correlation-inspection-influence { permissive | standard | aggressive }—Lets you choose the level of global correlation inspection. The default is standard.

permissive —Global correlation data has little influence in the decision to deny traffic.

standard—Global correlation moderately influences the decision to deny traffic.

aggressive—Global correlation data heavily influences the decision to deny traffic.

  • reputation-filtering {on | off} —Turns reputation filtering on or off. When turned on, the sensor denies access to malicious hosts that are listed in the global correlation database. The default is on.
  • test-global-correlation {on | off}—Enables reporting of deny actions that are affected by global correlation. Allows you to test the global correlation features without actually denying any hosts. The default is off.

Configuring Global Correlation

To configure global correlation features, follow these steps:


Step 1 Log in to the CLI using an account with administrator privileges.

Step 2 Enter global correlation submode.

sensor# configure terminal
sensor(config)# service global-correlation
sensor(config-glo)#
 

Step 3 Turn on global correlation inspection.

sensor(config-glo)# global-correlation-inspection on
sensor(config-glo)#
 

Step 4 Specify the level of global correlation inspection.

sensor(config-glo)# global-correlation-inspection-influence aggressive
sensor(config-glo)#
 

Step 5 Turn on reputation filtering.

sensor(config-glo)# reputation-filtering on
sensor(config-glo)#
 

Step 6 Test global correlation data, but do not actually deny traffic.

sensor(config-glo)# test-global-correlation on
sensor(config-glo)#
 

Step 7 Verify the settings.

sensor(config-glo)# show settings
global-correlation-inspection: on default: on
global-correlation-inspection-influence: aggressive default: standard
reputation-filtering: on default: on
test-global-correlation: on default: off
sensor(config-glo)#
 

Step 8 Exit global correlation submode.

sensor(config-glo)# exit
Apply Changes:?[yes]:
 

Step 9 Press Enter to apply your changes or enter no to discard them.


 

For More Information

Configuring Network Participation

You can configure the sensor to send data to the SensorBase Network. You can configure the sensor to fully participate and send all data to the SensorBase Network. Or you can configure the sensor to collect the data but to omit potentially sensitive data, such as the destination IP address of trigger packets.


Note Configuring the sensor for partial network participation limits a third party from extracting reconnaissance information about your internal network from the global correlation database.


The following option applies:

  • network-participation —Sets the level of network participation. The default is off.

off—No data is contributed to the SensorBase network.

partial—Data is contributed to the SensorBase network but potentially sensitive information is withheld.

full—All data is contributed to the SensorBase network.


Note You must accept the network participation disclaimer to turn on network participation.


Turning on Network Participation

To turn on network participation, follow these steps:


Step 1 Log in to the CLI using an account with administrator privileges.

Step 2 Enter global correlation submode.

sensor# configure terminal
sensor(config)# service global-correlation
sensor(config-glo)#
 

Step 3 Turn on network participation.

sensor(config-glo)# network-participation [full | partial]
sensor(config-glo)# exit
 

Step 4 Enter yes to agree to participate in the SensorBase Network.

If you agree to participate in the SensorBase Network, Cisco will collect aggregated statistics about traffic sent to your IPS. This includes summary data on the Cisco IPS network traffic properties and how this traffic was handled by the Cisco appliances. We do not collect the data content of traffic or other sensitive business or personal information. All data is aggregated and sent via secure HTTP to the Cisco SensorBase Network servers in periodic intervals. All data shared with Cisco will be anonymous and treated as strictly confidential.
The table below describes how the data will be used by Cisco.
Participation Level = "Partial":
* Type of Data: Protocol Attributes (e.g. TCP max segment size and
options string)
Purpose: Track potential threats and understand threat exposure
* Type of Data: Attack Type (e.g. Signature Fired and Risk Rating)
Purpose: Used to understand current attacks and attack severity
* Type of Data: Connecting IP Address and port
Purpose: Identifies attack source
* Type of Data: Summary IPS performance (CPU utilization memory usage,
inline vs. promiscuous, etc)
Purpose: Tracks product efficacy
Participation Level = "Full" additionally includes:
* Type of Data: Victim IP Address and port
Purpose: Detect threat behavioral patterns
 
Do you agree to participate in the SensorBase Network?[no]:
 

Step 5 Verify the settings.

sensor(config-glo)# show settings
network-participation: full default: off
global-correlation-inspection: on default: on
global-correlation-inspection-influence: aggressive default: standard
reputation-filtering: on default: on
test-global-correlation: on default: off
sensor(config-glo)#
 

Step 6 Exit global correlation submode.

sensor(config-glo)# exit
Apply Changes:?[yes]:
 

Step 7 Press Enter to apply your changes or enter no to discard them.


 

For More Information

For more information about participating in the SensorBase Network, see Participating in the SensorBase Network.

Troubleshooting Global Correlation

Make sure you observe the following when configuring global correlation:

  • Because global correlation updates occur through the sensor management interface, firewalls must allow port 443/80 traffic.
  • You must have an HTTP proxy server or a DNS server configured to allow global correlation features to function.
  • cYou must have a valid IPS license to allow global correlation features to function.
  • Global correlation features only contain external IP addresses, so if you position a sensor in an internal lab, you may never receive global correlation information.
  • Make sure your sensor supports the global correlation features.
  • Make sure your IPS version supports the global correlation features.

For More Information

Disabling Global Correlation

If your sensor is deployed in an environment where a DNS server or HTTP proxy server is not available, you may want to disable global correlation so that global correlation health does not appear as red in the overall sensor health, thus indicating a problem. You can also configure sensor health to exclude global correlation status.

The following options apply:

  • global-correlation-inspection {on | off} —Turns global correlation inspection on or off. When turned on, the sensor uses updates from the SensorBase network to adjust the risk rating. The default is on.
  • reputation-filtering {on | off} —Turns reputation filtering on or off. When turned on, the sensor denies access to malicious hosts that are listed in the global correlation database. The default is on.
  • network-participation —Sets the level of network participation. The default is off.

off—No data is contributed to the SensorBase network.

partial—Data is contributed to the SensorBase network but potentially sensitive information is withheld.

full—All data is contributed to the SensorBase network.

Disabling Global Correlation

To disable global correlation features, follow these steps:


Step 1 Log in to the CLI using an account with administrator privileges.

Step 2 Enter global correlation submode.

sensor# configure terminal
sensor(config)# service global-correlation
sensor(config-glo)#
 

Step 3 Turn off global correlation inspection.

sensor(config-glo)# global-correlation-inspection off
sensor(config-glo)#
 

Step 4 Turn off reputation filtering.

sensor(config-glo)# reputation-filtering off
sensor(config-glo)#
 

Step 5 Turn off network participation.

sensor(config-glo)# network-participation off
sensor(config-glo)# exit
 

Step 6 Verify the settings.

sensor(config-glo)# show settings
network-participation: full default: off
global-correlation-inspection: on default: off
reputation-filtering: on default: off
sensor(config-glo)#
 
 

Step 7 Exit global correlation submode.

sensor(config-glo)# exit
Apply Changes:?[yes]:
 

Step 8 Press Enter to apply your changes or enter no to discard them.


 

Displaying Global Correlation Statistics

Use the show statistics global-correlation command to display global correlation statistics. Use the show statistics global-correlation [ name | clear ] command to display statistics for these components for all virtual sensors. If you provide the virtual sensor name, the statistics for that virtual sensor only are displayed.


Note For IPS 7.0(7)E4 and later and IPS 7.1(5)E4 and later, the output includes any failures that have been detected.


To display and clear global correlation statistics for the sensor, follow these steps:


Step 1 Log in to the CLI.

Step 2 Display the statistics for global correlation.

sensor# show statistics global-correlation
Network Participation:
Counters:
Total Connection Attempts = 4347
Total Connection Failures = 155
Connection Failures Since Last Success = 0
Connection History:
Connection Attempt on June 17 2012, at 21:57:19 UTC = Successful
Connection Attempt on June 17 2012, at 21:54:18 UTC = Successful
Connection Attempt on June 17 2012, at 21:51:17 UTC = Successful
Connection Attempt on June 17 2012, at 21:48:17 UTC = Successful
Connection Attempt on June 17 2012, at 21:45:16 UTC = Successful
Updates:
Status Of Last Update Attempt = Disabled
Time Since Last Successful Update = never
Counters:
Update Failures Since Last Success = 0
Total Update Attempts = 0
Total Update Failures = 0
Update Interval In Seconds = 300
Update Server = update-manifests.ironport.com
Update Server Address = Unknown
Current Versions:
Warnings:
Details:
Last fail log =
sensor#
 

Step 3 Clear the statistics for global correlation:

sensor# show statistics global-correlation clear
Network Participation:
Counters:
Total Connection Attempts = 0
Total Connection Failures = 0
Connection Failures Since Last Success = 0
Connection History:
Connection Attempt on June 17 2012, at 22:03:20 UTC = Successful
Connection Attempt on June 17 2012, at 22:00:19 UTC = Successful
Connection Attempt on June 17 2012, at 21:57:19 UTC = Successful
Connection Attempt on June 17 2012, at 21:54:18 UTC = Successful
Connection Attempt on June 17 2012, at 21:51:17 UTC = Successful
Updates:
Status Of Last Update Attempt = Disabled
Time Since Last Successful Update = never
Counters:
Update Failures Since Last Success = 0
Total Update Attempts = 0
Total Update Failures = 0
Update Interval In Seconds = 300
Update Server = update-manifests.ironport.com
Update Server Address = Unknown
Current Versions:
Warnings:
Details:
Last fail log =
sensor#