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30 ServerIron ADX Security Guide
53-1002440-03
Logging for DoS Attacks
1
Logging for DoS Attacks
The following sections describe how to enable logging of DoS attacks.
Configuration commands
Use the following commands to enable logging of TCP connection rate and attack rate.
Syntax: [no] ip tcp conn-rate <rate> attack-rate <rate>
Syntax: [no] ip tcp conn-rate-change <percentage> attack-rate <percentage>
Syntax: [no] server max-conn-trap <seconds>
Parameters
The conn-rate <rate> parameter specifies a threshold for the number of global TCP connections
per second that are expected on the ServerIron. A global TCP connection is defined as any packet
that requires session processing. For example, 1 SLB, 1 TCS, and 1 SYN-Guard connection would
equal 3 global TCP connections, since there are three different connections that require session
processing.
NOTE
The ServerIron ADX counts only the new connections that remain in effect at the end of the one
second interval. If a connection is opened and terminated within the interval, the ServerIron ADX
does not include the connection in the total for the server.
The attack-rate <rate> parameter specifies a threshold for the number of TCP SYN attack packets
per second that are expected on the ServerIron.
Syslog entries are generated under the following circumstances:
• If the connection rate or attack rate on the ServerIron reaches 80% of the configured
threshold.
• If the connection rate or attack rate is still between 80% and 100% of the configured threshold
6 minutes after the last message.
• If the connection rate or attack rate exceeds 100% of the configured threshold.
• If the connection rate or attack rate exceeds 100% of the configured threshold, and has gone
up by the configured rate change percentage.
• One minute after the last message indicating that the connection rate or attack rate still
exceeds 100% of the configured threshold, and has gone up by the configured rate change
percentage.
• Three minutes after the last message, if the connection rate or attack rate is still between 80%
and 100% of the configured threshold, and has gone up by the configured rate change
percentage.
The server max-conn-trap <seconds> command specifies the number of seconds that elapse
between traps, where <seconds> can be from 1 to 300. The default is 30.
Example
ServerIronADX(config)# ip tcp conn-rate 10000 attack-rate 10000
ServerIronADX(config)# ip tcp conn-rate-change 50 attack-rate 100
ServerIronADX(config)# server max-conn-trap 30