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Kernel Hardening: Disable ICMP Redirects
MediumLinux Security10-15 minThe brief
ICMP redirects let an on-path attacker reroute your traffic. Harden the kernel by disabling accepted redirects — persistently, in a sysctl drop-in (a live sysctl -w is lost on reboot). Set net.ipv4.conf.all.accept_redirects to 0 under /etc/sysctl.d/, using the usual 'key = value' drop-in format.
Grading reads the sysctl configuration the way sysctl --system does.
What you'll do
- Persistently set net.ipv4.conf.all.accept_redirects = 0 in /etc/sysctl.d/
Hands-on lab: you work on a real Linux box in your browser, graded on the machine's actual state.