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RHEL 9 must not respond to Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-257966 | RHEL-09-253055 | SV-257966r991589_rule | Medium |
| 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. |
| STIG | Date |
|---|---|
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-06-04 |
Details
| Check Text ( C-61707r942994_chk ) |
|---|
| 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 Text (F-61631r925884_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 |