Rule version TOSS-05-000221 · STIG v1 · 2026-08-20
Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.
Verify TOSS 5 does not respond to ICMP echoes sent to a broadcast address using the following command:
$ sudo sysctl net.ipv4.icmp_echo_ignore_broadcasts
net.ipv4.icmp_echo_ignore_broadcasts = 1
If the returned line does not have a value of "1", or a line is not returned, this is a finding.
Check that the configuration files are present to enable this network parameter.
$ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|$)' | grep -F net.ipv4.icmp_echo_ignore_broadcasts | tail -1
net.ipv4.icmp_echo_ignore_broadcasts = 1
If "net.ipv4.icmp_echo_ignore_broadcasts" is not set to "1" or is missing, this is a finding.
Configure TOSS 5 to not respond to IPv4 ICMP echoes sent to a broadcast address.
Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory:
net.ipv4.icmp_echo_ignore_broadcasts = 1
Load settings from all system configuration files using the following command:
$ sudo sysctl --system