RHEL 10 must log Internet Protocol version 4 (IPv4) packets with impossible addresses.

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.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00074

Verify RHEL 10 logs IPv4 martian packets.

Check the value of the "net.ipv4.conf.all.log_martians" variable with the following command:

$ sudo sysctl net.ipv4.conf.all.log_martians net.ipv4.conf.all.log_martians = 1

If "net.ipv4.conf.all.log_martians" is not set to "1" or is missing, this is a finding.

Configure RHEL 10 to log martian packets on IPv4 interfaces.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/99-ipv4_log_martians.conf

Add the following line to the file:

net.ipv4.conf.all.log_martians=1

Reload settings from all system configuration files with the following command:

$ sudo sysctl --system