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The Red Hat Enterprise Linux operating system must not respond to Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.


Overview

Finding ID Version Rule ID IA Controls Severity
V-72287 RHEL-07-040630 SV-86911r2_rule Medium
Description
Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
STIG Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide 2019-03-08

Details

Check Text ( C-72521r2_chk )
Verify the system does not respond to IPv4 ICMP echoes sent to a broadcast address.

# grep net.ipv4.icmp_echo_ignore_broadcasts /etc/sysctl.conf /etc/sysctl.d/*

If " net.ipv4.icmp_echo_ignore_broadcasts" is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "1", this is a finding.

Check that the operating system implements the "icmp_echo_ignore_broadcasts" variable with the following command:

# /sbin/sysctl -a | grep 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 Text (F-78641r2_fix)
Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value):

net.ipv4.icmp_echo_ignore_broadcasts = 1

Issue the following command to make the changes take effect:

# sysctl --system