The system must not send IPv4 Internet Control Message Protocol (ICMP) redirects.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-001551

SV-64205r1_rule The system must not send IPv4 Internet Control Message Protocol (ICMP) redirects.

Vulnerability discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.

Check content

Verify the system does not send IPv4 ICMP redirect messages. # grep [01] /proc/sys/net/ipv4/conf/*/send_redirects|egrep "default|all" If all of the resulting lines do not end with "0", this is a finding.

Fix text

Configure the system to not send IPv4 ICMP redirect messages. Edit /etc/sysctl.conf and add a setting for "net.ipv4.conf.all.send_redirects=0" and "net.ipv4.conf.default.send_redirects=0". # sysctl -p

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