# Cis Ubuntu2004 V300 4 2 1

> Ensure ufw is installed

- Skill: `cyberstrikeus/cis-ubuntu2004-v300-4-2-1` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu2004-v300-4-2-1`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu2004-v300-4-2-1/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu2004-v300-4-2-1

---


# CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0 - Control 4.2.1

## Profile

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

## Description

The Uncomplicated Firewall (ufw) is a frontend for iptables and is particularly well-suited for host-based firewalls. ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall

## Rationale

A firewall utility is required to configure the Linux kernel's netfilter framework via the iptables or nftables back-end.

The Linux kernel's netfilter framework host-based firewall can protect against threats originating from within a corporate network to include malicious mobile code and poorly configured software on a host.

Note: Only one firewall utility should be installed and configured. UFW is dependent on the iptables package

## Audit Procedure

### Command Line

Run the following command to verify that Uncomplicated Firewall (UFW) is installed:

```bash
dpkg-query -s ufw &>/dev/null && echo "ufw is installed"
```

## Expected Result

```
ufw is installed
```

## Remediation

### Command Line

Run the following command to install Uncomplicated Firewall (UFW):

```bash
apt install ufw
```

## Default Value

Not applicable.

## References

1. NIST SP 800-53 Rev. 5: SC-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 | TA0011 | M1031, M1037