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RHEL 9 must log IPv4 packets with impossible addresses.


Overview

Finding ID Version Rule ID IA Controls Severity
V-257960 RHEL-09-253025 SV-257960r991589_rule Medium
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.
STIG Date
Red Hat Enterprise Linux 9 Security Technical Implementation Guide 2024-06-04

Details

Check Text ( C-61701r925865_chk )
Verify RHEL 9 logs IPv4 martian packets.

Check the value of the accept source route variable with the following command:

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

net.ipv4.conf.all.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.

Check that the configuration files are present to enable this network parameter.

$ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F net.ipv4.conf.all.log_martians | tail -1

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.
Fix Text (F-61625r925866_fix)
Configure RHEL 9 to log martian packets on IPv4 interfaces.

Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory:

net.ipv4.conf.all.log_martians=1

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

$ sudo sysctl --system