Lynis Security Controls
FIRE-4513 - Unused iptables rules
This control checks what iptables rules are currently not being used. Proper maintenance of firewall rules is essential for accuracy and proper network traffic filtering. Regular checks on the proper working and rule-sets help in limiting traffic to the bare minimum and decrease general risk of unauthorized connections. Note: Some rules might have no hits, while still being applicable. Before removing rules, make sure that the time to monitor is long enough.
How to solve
Use iptables --list --numeric --verbose to display all rules. Check for rules which didn't get a hit and repeat this process several times (e.g. in a few weeks). Finally remove any unneeded rules.
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Linux and Unix System Hardening
This information is provided as part of the Lynis community project. It is related to Lynis control FIRE-4513. All information should be considered as-is, without guarantees. Any advice or snippets should be tested before implementing in production environments.
Lynis is a technical security audit tool for Unix flavors like Linux, macOS, AIX, Solaris, and *BSD. It is open source software and free to use. The project has an active community, including open development via GitHub.
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