3.2.4 Ensure suspicious packets are logged

Information

When enabled, this feature logs packets with un-routable source addresses to the kernel log.

Rationale:

Enabling this feature and logging these packets allows an administrator to investigate the possibility that an
attacker is sending spoofed packets to their system.

Solution

Run the following command to set the active kernel parameters and persist the settings:

# apiclient apply <<EOF
[settings.kernel.sysctl]
"net.ipv4.conf.all.log_martians" = "1"
"net.ipv4.conf.default.log_martians" = "1"
EOF

Run the following command to flush the routing cache:

# sysctl -w net.ipv4.route.flush=1

See Also

https://workbench.cisecurity.org/benchmarks/6709