Threat Detection

This chapter describes how to configure threat detection statistics and scanning threat detection and includes the following sections:

Information About Threat Detection

The threat detection feature consists of the following elements:

  • Different levels of statistics gathering for various threats.

Threat detection statistics can help you manage threats to your ASA; for example, if you enable scanning threat detection, then viewing statistics can help you analyze the threat. You can configure two types of threat detection statistics:

– Basic threat detection statistics—Includes information about attack activity for the system as a whole. Basic threat detection statistics are enabled by default and have no performance impact.

– Advanced threat detection statistics—Tracks activity at an object level, so the ASA can report activity for individual hosts, ports, protocols, or ACLs. Advanced threat detection statistics can have a major performance impact, depending on the statistics gathered, so only the ACL statistics are enabled by default.

  • Scanning threat detection, which determines when a host is performing a scan.

You can optionally shun any hosts determined to be a scanning threat.

Licensing Requirements for Threat Detection

The following table shows the licensing requirements for this feature:

 

Model
License Requirement

ASAv

Standard or Premium License.

All other models

Base License.

Configuring Basic Threat Detection Statistics

Basic threat detection statistics include activity that might be related to an attack, such as a DoS attack.

This section includes the following topics:

Information About Basic Threat Detection Statistics

Using basic threat detection statistics, the ASA monitors the rate of dropped packets and security events due to the following reasons:

  • Denial by ACLs
  • Bad packet format (such as invalid-ip-header or invalid-tcp-hdr-length)
  • Connection limits exceeded (both system-wide resource limits, and limits set in the configuration)
  • DoS attack detected (such as an invalid SPI, Stateful Firewall check failure)
  • Basic firewall checks failed (This option is a combined rate that includes all firewall-related packet drops in this bulleted list. It does not include non-firewall-related drops such as interface overload, packets failed at application inspection, and scanning attack detected.)
  • Suspicious ICMP packets detected
  • Packets failed application inspection
  • Interface overload
  • Scanning attack detected (This option monitors scanning attacks; for example, the first TCP packet is not a SYN packet, or the TCP connection failed the 3-way handshake. Full scanning threat detection (see Configuring Scanning Threat Detection) takes this scanning attack rate information and acts on it by classifying hosts as attackers and automatically shunning them, for example.)
  • Incomplete session detection such as TCP SYN attack detected or no data UDP session attack detected

When the ASA detects a threat, it immediately sends a system log message (733100). The ASA tracks two types of rates: the average event rate over an interval, and the burst event rate over a shorter burst interval. The burst rate interval is 1/30th of the average rate interval or 10 seconds, whichever is higher. For each received event, the ASA checks the average and burst rate limits; if both rates are exceeded, then the ASA sends two separate system messages, with a maximum of one message for each rate type per burst period.

Basic threat detection affects performance only when there are drops or potential threats; even in this scenario, the performance impact is insignificant.

Guidelines and Limitations

This section includes the guidelines and limitations for this feature:

Security Context Guidelines

Supported in single mode only. Multiple mode is not supported.

Firewall Mode Guidelines

Supported in routed and transparent firewall mode.

Types of Traffic Monitored

Only through-the-box traffic is monitored; to-the-box traffic is not included in threat detection.

Default Settings

Basic threat detection statistics are enabled by default.

Table 25-1 lists the default settings. You can view all these default settings using the show running-config all threat-detection command in Tools > Command Line Interface.

 

Table 25-1 Basic Threat Detection Default Settings

Packet Drop Reason
Trigger Settings
Average Rate
Burst Rate
  • DoS attack detected
  • Bad packet format
  • Connection limits exceeded
  • Suspicious ICMP packets detected

100 drops/sec over the last 600 seconds.

400 drops/sec over the last 20 second period.

80 drops/sec over the last 3600 seconds.

320 drops/sec over the last 120 second period.

Scanning attack detected

5 drops/sec over the last 600 seconds.

10 drops/sec over the last 20 second period.

4 drops/sec over the last 3600 seconds.

8 drops/sec over the last 120 second period.

Incomplete session detected such as TCP SYN attack detected or no data UDP session attack detected (combined)

100 drops/sec over the last 600 seconds.

200 drops/sec over the last 20 second period.

80 drops/sec over the last 3600 seconds.

160 drops/sec over the last 120 second period.

Denial by ACLs

400 drops/sec over the last 600 seconds.

800 drops/sec over the last 20 second period.

320 drops/sec over the last 3600 seconds.

640 drops/sec over the last 120 second period.
  • Basic firewall checks failed
  • Packets failed application inspection

400 drops/sec over the last 600 seconds.

1600 drops/sec over the last 20 second period.

320 drops/sec over the last 3600 seconds.

1280 drops/sec over the last 120 second period.

Interface overload

2000 drops/sec over the last 600 seconds.

8000 drops/sec over the last 20 second period.

1600 drops/sec over the last 3600 seconds.

6400 drops/sec over the last 120 second period.

Configuring Basic Threat Detection Statistics

This section describes how to configure basic threat detection statistics, including enabling or disabling it and changing the default limits.

Detailed Steps

Step 1 To enable or disable basic threat detection, choose the Configuration > Firewall > Threat Detection pane, and check the Enable Basic Threat Detection check box.

Step 2 Click Apply.

 

Monitoring Basic Threat Detection Statistics

To monitor basic threat detection statistics, perform the following task:

 

Path
Purpose

Home > Firewall Dashboard > Traffic Overview

Displays basic threat detection statistics.

For a description of each event type, see Information About Basic Threat Detection Statistics.

Feature History for Basic Threat Detection Statistics

Table 25-2 lists each feature change and the platform release in which it was implemented. ASDM is backwards-compatible with multiple platform releases, so the specific ASDM release in which support was added is not listed.

 

Table 25-2 Feature History for Basic Threat Detection Statistics
Feature Name
Platform Releases
Feature Information

Basic threat detection statistics

8.0(2)

Basic threat detection statistics was introduced.

The following screen was introduced: Configuration > Firewall > Threat Detection, Home > Firewall Dashboard > Traffic Overview.

Burst rate interval changed to 1/30th of the average rate.

8.2(1)

In earlier releases, the burst rate interval was 1/60th of the average rate. To maximize memory usage, the sampling interval was reduced to 30 times during the average rate.

Improved memory usage

8.3(1)

The memory usage for threat detection was improved.

Configuring Advanced Threat Detection Statistics

You can configure the ASA to collect extensive statistics. This section includes the following topics:

Information About Advanced Threat Detection Statistics

Advanced threat detection statistics show both allowed and dropped traffic rates for individual objects such as hosts, ports, protocols, or ACLs.

Caution En abling advanced statistics can affect the ASA performance, depending on the type of statistics enabled. Enabling host statistics affects performance in a significant way; if you have a high traffic load, you might consider enabling this type of statistics temporarily. Port statistics, however, has modest impact.

Guidelines and Limitations

This section includes the guidelines and limitations for this feature:

Security Context Guidelines

Only TCP Intercept statistics are available in multiple mode.

Firewall Mode Guidelines

Supported in routed and transparent firewall mode.

Types of Traffic Monitored

Only through-the-box traffic is monitored; to-the-box traffic is not included in threat detection.

Default Settings

By default, statistics for ACLs are enabled.

Configuring Advanced Threat Detection Statistics

By default, statistics for ACLs are enabled. To enable other statistics, perform the following steps.

Detailed Steps

 

Step 1 Choose the Configuration > Firewall > Threat Detection pane.

Step 2 In the Scanning Threat Statistics area, choose one of the following options:

    • Enable all statistics—Click the Enable All Statistics radio button.
  • Disable all statistics—Click the Disable All Statistics radio button.
  • Enable only certain statistics—Click the Enable Only Following Statistics radio button.

Step 3 If you chose to Enable Only Following Statistics, then check one or more of the following check boxes:

    • Hosts —Enables host statistics. The host statistics accumulate for as long as the host is active and in the scanning threat host database. The host is deleted from the database (and the statistics cleared) after 10 minutes of inactivity.
    • Access Rules (enabled by default)—Enables statistics for access rules.
    • Port —Enables statistics for TCP and UDP ports.
    • Protocol —Enables statistics for non-TCP/UDP IP protocols.
    • TCP-Intercept —Enables statistics for attacks intercepted by TCP Intercept (see Configuring Connection Settings to enable TCP Intercept).

Step 4 For host, port, and protocol statistics, you can change the number of rate intervals collected. In the Rate Intervals area, choose 1 hour, 1 and 8 hours, or 1, 8 and 24 hours for each statistics type. The default interval is 1 hour, which keeps the memory usage low.

Step 5 For TCP Intercept statistics, you can set the following options in the TCP Intercept Threat Detection area:

    • Monitoring Window Size —Sets the size of the history monitoring window, between 1 and 1440 minutes. The default is 30 minutes. The ASA samples the number of attacks 30 times during the rate interval, so for the default 30 minute period, statistics are collected every 60 seconds.
    • Burst Threshold Rate —Sets the threshold for syslog message generation, between 25 and 2147483647. The default is 400 per second. When the burst rate is exceeded, syslog message 733104 is generated.
    • Average Threshold Rate —Sets the average rate threshold for syslog message generation, between 25 and 2147483647. The default is 200 per second. When the average rate is exceeded, syslog message 733105 is generated.

Click Set Default to restore the default values.

Step 6 Click Apply.

 

Monitoring Advanced Threat Detection Statistics

To monitor advanced threat detection statistics, perform one of the following tasks:

 

Path
Purpose

Home > Firewall Dashboard > Top 10 Access Rules

Home > Firewall Dashboard > Top Usage Statistics

Displays the top 10 statistics.

For the Top 10 Access Rules, permitted and denied traffic are not differentiated in this display. In the Traffic Overview > Dropped Packets Rate graph, you can track ACL denies.

The Top 10 Sources and Top 10 Destinations tabs show statistics for hosts. Note : Due to the threat detction algorithm, an interface used as a combination failover and state link could appear in the top 10 hosts; this is expected behavior, and you can ignore this IP address in the display.

The Top 10 Services tab shows statistics for both ports and protocols (both must be enabled for the display), and shows the combined statistics of TCP/UDP port and IP protocol types. TCP (protocol 6) and UDP (protocol 17) are not included in the display for IP protocols; TCP and UDP ports are, however, included in the display for ports. If you only enable statistics for one of these types, port or protocol, then you will only view the enabled statistics.

The Top Ten Protected Servers under SYN Attack area shows the TCP Intercept statistics. The display includes the top 10 protected servers under attack. The detail button shows history sampling data. The ASA samples the number of attacks 30 times during the rate interval, so for the default 30 minute period, statistics are collected every 60 seconds.

From the Interval drop-down list, choose Last 1 hour, Last 8 hour, or Last 24 hour.

Feature History for Advanced Threat Detection Statistics

Table 25-3 lists each feature change and the platform release in which it was implemented. ASDM is backwards-compatible with multiple platform releases, so the specific ASDM release in which support was added is not listed.

 

Table 25-3 Feature History for Advanced Threat Detection Statistics

Feature Name
Platform Releases
Feature Information

Advanced threat detection statistics

8.0(2)

Advanced threat detection statistics was introduced.

The following screens were introduced: Configuration > Firewall > Threat Detection, Home > Firewall Dashboard > Top 10 Access Rules, Home > Firewall Dashboard > Top Usage Status, Home > Firewall Dashboard > Top 10 Protected Servers Under SYN Attack.

TCP Intercept statistics

8.0(4)/8.1(2)

TCP Intercept statistics were introduced.

The following screens were introduced or modified: Configuration > Firewall > Threat Detection, Home > Firewall Dashboard > Top 10 Protected Servers Under SYN Attack.

Customize host statistics rate intervals

8.1(2)

You can now customize the number of rate intervals for which statistics are collected. The default number of rates was changed from 3 to 1.

The following screen was modified: Configuration > Firewall > Threat Detection.

Burst rate interval changed to 1/30th of the average rate.

8.2(1)

In earlier releases, the burst rate interval was 1/60th of the average rate. To maximize memory usage, the sampling interval was reduced to 30 times during the average rate.

Customize port and protocol statistics rate intervals

8.3(1)

You can now customize the number of rate intervals for which statistics are collected. The default number of rates was changed from 3 to 1.

The following screen was modified: Configuration > Firewall > Threat Detection.

Improved memory usage

8.3(1)

The memory usage for threat detection was improved.

Configuring Scanning Threat Detection

This section includes the following topics:

Information About Scanning Threat Detection

A typical scanning attack consists of a host that tests the accessibility of every IP address in a subnet (by scanning through many hosts in the subnet or sweeping through many ports in a host or subnet). The scanning threat detection feature determines when a host is performing a scan. Unlike IPS scan detection that is based on traffic signatures, the ASA scanning threat detection feature maintains an extensive database that contains host statistics that can be analyzed for scanning activity.

The host database tracks suspicious activity such as connections with no return activity, access of closed service ports, vulnerable TCP behaviors such as non-random IPID, and many more behaviors.

If the scanning threat rate is exceeded, then the ASA sends a syslog message (733101), and optionally shuns the attacker. The ASA tracks two types of rates: the average event rate over an interval, and the burst event rate over a shorter burst interval. The burst event rate is 1/30th of the average rate interval or 10 seconds, whichever is higher. For each event detected that is considered to be part of a scanning attack, the ASA checks the average and burst rate limits. If either rate is exceeded for traffic sent from a host, then that host is considered to be an attacker. If either rate is exceeded for traffic received by a host, then that host is considered to be a target.

Caution The scanning threat detection feature can affect th e ASA performance and memory significantly while it creates and gathers host- and subnet-based data structure and information.

Guidelines and Limitations

This section includes the guidelines and limitations for this feature:

Security Context Guidelines

Supported in single mode only. Multiple mode is not supported.

Firewall Mode Guidelines

Supported in routed and transparent firewall mode.

Types of Traffic Monitored

  • Only through-the-box traffic is monitored; to-the-box traffic is not included in threat detection.
  • Traffic that is denied by an ACL does not trigger scanning threat detection; only traffic that is allowed through the ASA and that creates a flow is affected by scanning threat detection.

Default Settings

Table 25-4 lists the default rate limits for scanning threat detection.

 

Table 25-4 Default Rate Limits for Scanning Threat Detection
Average Rate
Burst Rate

5 drops/sec over the last 600 seconds.

10 drops/sec over the last 20 second period.

5 drops/sec over the last 3600 seconds.

10 drops/sec over the last 120 second period.

The burst rate is calculated as the average rate every N seconds, where N is the burst rate interval. The burst rate interval is 1/30th of the rate interval or 10 seconds, whichever is larger.

Configuring Scanning Threat Detection

Detailed Steps

 

Step 1 Choose the Configuration > Firewall > Threat Detection pane, and check the Enable Scanning Threat Detection check box.

Step 2 (Optional) To automatically terminate a host connection when the ASA identifies the host as an attacker, check the Shun Hosts detected by scanning threat check box.

Step 3 (Optional) To except host IP addresses from being shunned, enter an address in the Networks excluded from shun field.

You can enter multiple addresses or subnets separated by commas. To choose a network from the list of IP address objects, click the ... button.

Step 4 (Optional) To set the duration of a shun for an attacking host, check the Set Shun Duration check box and enter a value between 10 and 2592000 seconds. The default length is 3600 seconds (1 hour). To restore the default value, click Set Default.

 

Feature History for Scanning Threat Detection

Table 25-5 lists each feature change and the platform release in which it was implemented. ASDM is backwards-compatible with multiple platform releases, so the specific ASDM release in which support was added is not listed.

 

Table 25-5 Feature History for Scanning Threat Detection

Feature Name
Platform Releases
Feature Information

Scanning threat detection

8.0(2)

Scanning threat detection was introduced.

The following screen was introduced: Configuration > Firewall > Threat Detection.

Shun duration

8.0(4)/8.1(2)

You can now set the shun duration,

The following screen was modified: Configuration > Firewall > Threat Detection.

Burst rate interval changed to 1/30th of the average rate.

8.2(1)

In earlier releases, the burst rate interval was 1/60th of the average rate. To maximize memory usage, the sampling interval was reduced to 30 times during the average rate.

Improved memory usage

8.3(1)

The memory usage for threat detection was improved.