Title

SLEM 5 must not allow interfaces to send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages by default. (Cat II impact)

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 SLEM 5 does not allow interfaces to perform IPv4 ICMP redirects by default with the following command: > sudo sysctl net.ipv4.conf.default.send_redirects net.ipv4.conf.default.send_redirects = 0 If the network parameter "ipv4.conf.default.send_redirects" is not equal to "0", or nothing is returned, this is a finding.

Fix Text

Configure SLEM 5 to not allow interfaces to perform IPv4 ICMP redirects by default by running the following command as an administrator: > sudo sysctl -w net.ipv4.conf.default.send_redirects=0 If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf": > sudo sh -c 'echo "net.ipv4.conf.default.send_redirects=0" >> /etc/sysctl.d/99-stig.conf' > sudo sysctl --system

Additional Identifiers

Rule ID: SV-261318r996424_rule

Vulnerability ID: V-261318

Group Title: SRG-OS-000480-GPOS-00227

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