OL 9 must log IPv4 packets with impossible addresses by default.

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.

Verify that OL 9 logs IPv4 martian packets by default. Check the value of the accept source route variable with the following command: $ sysctl net.ipv4.conf.default.log_martians net.ipv4.conf.default.log_martians = 1 If the returned line does not have a value of "1", a line is not returned, or the line is commented out, this is a finding.

Configure OL 9 to log martian packets on IPv4 interfaces by default. Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory: net.ipv4.conf.default.log_martians=1 Load settings from all system configuration files with the following command: $ sudo sysctl --system