CLI Reference Guide-R04

Chapter 9 | General Security Measures
Denial of Service Protection
– 374 –
Example
Console(config)#dos-protection land
Console(config)#
dos-protection
tcp-null-scan
This command protects against TCP-null-scan attacks in which a TCP NULL scan
message is used to identify listening TCP ports. The scan uses a series of strangely
configured TCP packets which contain a sequence number of 0 and no flags. If the
target's TCP port is closed, the target replies with a TCP RST (reset) packet. If the
target TCP port is open, it simply discards the TCP NULL scan. Use the no form to
disable this feature.
Syntax
[no] dos-protection tcp-null-scan
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
In these packets, all TCP flags are 0.
Example
Console(config)#dos-protection tcp-null-scan
Console(config)#
dos-protection
tcp-syn-fin-scan
This command protects against DoS TCP-SYN/FIN-scan attacks in which a TCP SYN/
FIN scan message is used to identify listening TCP ports. The scan uses a series of
strangely configured TCP packets which contain SYN (synchronize) and FIN (finish)
flags. If the target's TCP port is closed, the target replies with a TCP RST (reset)
packet. If the target TCP port is open, it simply discards the TCP SYN FIN scan. Use
the no form to disable this feature.
Syntax
[no] dos-protection tcp-syn-fin-scan
Default Setting
Disabled
Command Mode
Global Configuration