cis-ubuntu2004-v300-4-2-2

name	cis-ubuntu2004-v300-4-2-2
description	Ensure nftables is not in use with ufw
category	cis-networking
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","firewall","ufw"]
cis_id	4.2.2
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0 - Control 4.2.2

Profile

• Level: Level 1 - Server, Level 1 - Workstation
• Assessment Status: Automated

Description

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables.

Rationale

Running both ufw and nftables may lead to conflict.

Audit Procedure

Command Line

Run the following commend to verify that nftables is not installed:

dpkg-query -s nftables &>/dev/null && echo "nftables is installed"

Nothing should be returned

• OR - Run the following command to verify nftables.service is not enabled:

systemctl is-enabled nftables.service 2>/dev/null | grep '^enabled'

Nothing should be returned Run the following command to verify nftables.service is not active:

systemctl is-active nftables.service 2>/dev/null | grep '^active'

Nothing should be returned

Expected Result

No output from any of the above commands.

Remediation

Command Line

Run the following command to remove nftables:

apt purge nftables

• OR - Run the following commands to stop and mask nftables.service:

systemctl stop nftables.service
systemctl mask nftables.service

Default Value

Not applicable.

References

1. NIST SP 800-53 Rev. 5: CA-9, CM-7

CIS Controls

v8 - 4.4 Implement and Manage a Firewall on Servers v8 - 4.5 Implement and Manage a Firewall on End-User Devices v7 - 9.4 Apply Host-based Firewalls or Port Filtering

MITRE ATT&CK Mappings: T1562, T1562.004 | TA0005 | M1033