The system must not respond to ICMPv4 sent to a broadcast address.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-38535	RHEL-06-000092	SV-50336r2_rule		Low

Description
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 6 Security Technical Implementation Guide	2016-12-16

Details

Check Text ( C-46093r2_chk )
The status of the "net.ipv4.icmp_echo_ignore_broadcasts" kernel parameter can be queried by running the following command: $ sysctl net.ipv4.icmp_echo_ignore_broadcasts The output of the command should indicate a value of "1". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf". $ grep net.ipv4.icmp_echo_ignore_broadcasts /etc/sysctl.conf If the correct value is not returned, this is a finding.

Check Text ( C-46093r2_chk )

The status of the "net.ipv4.icmp_echo_ignore_broadcasts" kernel parameter can be queried by running the following command:

$ sysctl net.ipv4.icmp_echo_ignore_broadcasts

The output of the command should indicate a value of "1". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf".

$ grep net.ipv4.icmp_echo_ignore_broadcasts /etc/sysctl.conf

If the correct value is not returned, this is a finding.

Fix Text (F-43483r1_fix)
To set the runtime status of the "net.ipv4.icmp_echo_ignore_broadcasts" kernel parameter, run the following command: # sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1 If this is not the system's default value, add the following line to "/etc/sysctl.conf": net.ipv4.icmp_echo_ignore_broadcasts = 1