# Cis Ubuntu2004 V300 4 2 2

> Ensure nftables is not in use with ufw

- Skill: `cyberstrikeus/cis-ubuntu2004-v300-4-2-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu2004-v300-4-2-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu2004-v300-4-2-2/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-v300-4-2-2

---


# 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:

```bash
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:

```bash
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:

```bash
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`:

```bash
apt purge nftables
```

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

```bash
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