AlmaLinux OS 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-269248 | ALMA-09-019050 | SV-269248r1050130_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 |
| CloudLinux AlmaLinux OS 9 Security Technical Implementation Guide | 2025-05-22 |
Details
| Check Text (C-73279r1049376_chk) |
| Verify AlmaLinux OS 9 does not respond to ICMP echoes sent to a broadcast address with the following command: $ 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", this is a finding. |
| Fix Text (F-73180r1049377_fix) |
| Configure AlmaLinux OS 9 to use reverse path filtering on all IP interfaces. Create a numbered *.conf file in /etc/sysctl.d/ with the following content: net.ipv4.icmp_echo_ignore_broadcasts = 1 The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command: $ sysctl –system |