FIRE-4513 - Unused iptables rules

(Firewall)

This information is provided as part of the Lynis community project. It is related to Lynis control FIRE-4513 and should be considered as-is and without guarantees. Any advice and commands should be tested before implementing them in production environments.

Description

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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About

Lynis is a technical security auditing tool for Unix flavors like Linux, macOS, AIX, Solaris, and *BSD. It is open source software and free to use. Typical usage include system hardening, compliance testing, and vulnerability scanning. The project has an active community, including development via GitHub.

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