cis-ubuntu1804-v220-3-3-3

name	cis-ubuntu1804-v220-3-3-3
description	Ensure bogus ICMP responses are ignored
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","networking","kernel-parameter"]
cis_id	3.3.3
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 3.3.3

Description

Setting icmp_ignore_bogus_error_responses to 1 prevents the kernel from logging bogus responses (RFC-1122 non-compliant) from broadcast reframes, keeping file systems from filling up with useless log messages.

Rationale

Some routers (and some attackers) will send responses that violate RFC-1122 and attempt to fill up a log file system with many useless error messages.

Impact

None.

Audit Procedure

Command Line

Run the following command to verify bogus ICMP responses are ignored:

sysctl net.ipv4.icmp_ignore_bogus_error_responses

grep -E '^\s*net\.ipv4\.icmp_ignore_bogus_error_responses\s*=\s*1\b' /etc/sysctl.conf /etc/sysctl.d/*.conf

Expected Result

net.ipv4.icmp_ignore_bogus_error_responses = 1

Remediation

Command Line

Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:

net.ipv4.icmp_ignore_bogus_error_responses = 1

Run the following commands to set the active kernel parameters:

sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
sysctl -w net.ipv4.route.flush=1

Default Value

net.ipv4.icmp_ignore_bogus_error_responses = 1

References

1. NIST SP 800-53 Rev. 5: CM-7, SC-5
2. CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0

CIS Controls

Version 8

4.1 Establish and Maintain a Secure Configuration Process - Establish and maintain a secure configuration process for enterprise assets.

Version 7

5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software.

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Assessment Status

Automated