TOSS 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-253128	TOSS-04-040870	SV-253128r825056_rule		Medium

Description

Responding to broadcast ICMP echoes facilitates network mapping and provides a vector for amplification attacks. There are notable differences between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). IPv6 does not implement the same method of broadcast as IPv4. Instead, IPv6 uses multicast addressing to the all-hosts multicast group. Refer to RFC4294 for an explanation of "IPv6 Node Requirements", which resulted in this difference between IPv4 and IPv6.

STIG	Date
Tri-Lab Operating System Stack (TOSS) 4 Security Technical Implementation Guide	2022-08-29

Details

Check Text ( C-56581r825054_chk )

Verify TOSS does not respond to ICMP echoes sent to a broadcast address. Note: If IPv4 is disabled on the system, this requirement is Not Applicable. Check the value of the "icmp_echo_ignore_broadcasts" variable with the following command: $ sudo 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", a line is not returned, or the retuned line is commented out, this is a finding.

Fix Text (F-56531r825055_fix)
Configure TOSS to not respond to IPv4 ICMP echoes sent to a broadcast address with the following command: $ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1 If "1" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d": net.ipv4.icmp_echo_ignore_broadcasts=1