IT Best Practices Tip: nist_V-38528
Severity: low
Short Description
The system must log Martian packets.
Long Description
The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.
How to Check Correct Configuration
The status of the "net.ipv4.conf.all.log_martians" kernel parameter can be queried by running the following command:
$ sysctl net.ipv4.conf.all.log_martians
The output of the command should indicate a value of "1". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf".
$ grep net.ipv4.conf.all.log_martians /etc/sysctl.conf
If the correct value is not returned, this is a finding.
How to Fix
To set the runtime status of the "net.ipv4.conf.all.log_martians" kernel parameter, run the following command:
# sysctl -w net.ipv4.conf.all.log_martians=1
If this is not the system's default value, add the following line to "/etc/sysctl.conf":
net.ipv4.conf.all.log_martians = 1