RHEL 9 must not respond to Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-257966 | SRG-OS-000480-GPOS-00227 | RHEL-09-253055 | SV-257966r991589_rule | 2025-02-27 | 2 |
| Description |
|---|
| 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. |
| ℹ️ Check |
|---|
| Verify RHEL 9 does not respond to ICMP echoes sent to a broadcast address. Check the value of the "icmp_echo_ignore_broadcasts" variable with 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", a line is not returned, or the retuned line is commented out, 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. |
| ✔️ Fix |
|---|
| Configure RHEL 9 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 with the following command: $ sudo sysctl --system |