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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-208860	OL6-00-000092	SV-208860r505921_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
Oracle Linux 6 Security Technical Implementation Guide	2020-09-10

Details

Check Text ( C-9113r357560_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-9113r357560_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-9113r357561_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