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