Disable ICMP Redirect Acceptance ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will not accept any ICMP redirect messages, and therefore, won't allow outsiders to update the system's routing tables. [no/yes] Attackers could use bogus ICMP redirect messages to maliciously alter the system routing tables and get them to send packets to incorrect networks and allow your system packets to be captured. Fix: Set the net.ipv4.conf.all.accept_redirects and net.ipv4.conf.default.accept_redirects parameters to 0 in /etc/sysctl.conf: net.ipv4.conf.all.accept_redirects=0 net.ipv4.conf.default.accept_redirects=0 Modify active kernel parameters to match: # /sbin/sysctl -w net.ipv4.conf.all.accept_redirects=0 # /sbin/sysctl -w net.ipv4.conf.default.accept_redirects=0 # /sbin/sysctl -w net.ipv4.route.flush=1 oval:org.secpod.oval:def:55117 SCAP Repo OVAL Definition 2019-06-19