ALMA-09-019050 - AlmaLinux OS 9 must not respond to Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.

Information

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.

Solution

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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_CL_AlmaLinux_OS_9_V1R2_STIG.zip

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-269248r1050130_rule, STIG-ID|ALMA-09-019050, Vuln-ID|V-269248

Plugin: Unix

Control ID: 39b4e2ce8ed541037ef91197a3143c0661b711f121076f47e20e8c0dfb9e7357