AlmaLinux OS 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-269248 | SRG-OS-000480-GPOS-00227 | ALMA-09-019050 | SV-269248r1050130_rule | 2025-02-20 | 1 |
| 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 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 |
|---|
| 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 |