cis-ubuntu2004-v300-4-1-1

name	cis-ubuntu2004-v300-4-1-1
description	Ensure a single firewall configuration utility is in use
category	cis-networking
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","firewall","ufw","nftables","iptables"]
cis_id	4.1.1
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 4.1.1

Profile

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

Description

In Linux security, employing a single, effective firewall configuration utility ensures that only legitimate traffic gets processed, reducing the system's exposure to potential threats. The choice between ufw, nftables, and iptables depends on organizational needs.

Note: iptables is being phased out, and support for iptables will be reduced over time. It is recommended to transition towards either nftables or ufw as the default firewall management tool.

Rationale

Proper configuration of a single firewall utility minimizes cyber threats and protects services and data, while avoiding vulnerabilities like open ports or exposed services. Standardizing on a single tool simplifies management, reduces errors, and fortifies security across Linux systems.

Impact

The use of more than one firewall utility may produce unexpected results.

Audit Procedure

Command Line

Run the following script to verify that a single firewall utility is in use on the system:

#!/usr/bin/env bash

{
  active_firewall=() firewalls=("ufw" "nftables" "iptables")
  # Determine which firewall is in use
  for firewall in "${firewalls[@]}"; do
    case $firewall in
      nftables)
        cmd="nft" ;;
      *)
        cmd=$firewall ;;
    esac
    if command -v $cmd &> /dev/null && systemctl is-enabled --quiet $firewall && systemctl is-active --quiet $firewall; then
      active_firewall+=()
    
  
  
   [  -eq 1 ]; 
         
   [  -eq 0 ]; 
         
  
         
  
}