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cis-ubuntu1804-v220-3-4-2-2

DevOps & Security
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Ensure ufw is uninstalled or disabled with nftables

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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_18.04_LTS_Benchmark_v2.2.0/cis-ubuntu1804-v220-3-4-2-2/SKILL.md

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CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 3.4.2.2

Description

Uncomplicated Firewall (ufw) is a frontend for iptables. ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall.

Rationale

Running both the nftables service and ufw may lead to conflict.

Impact

None.

Audit Procedure

Command Line

Run the following command to verify that ufw is either not installed or disabled. Only one of the following needs to pass:

Run the following command to verify that ufw is not installed:

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

Nothing should be returned.

Run the following command to verify ufw is disabled:

ufw status

Expected output: Status: inactive

Run the following command to verify that the ufw service is masked:

systemctl is-enabled ufw

Expected output: masked

Expected Result

ufw is not installed, or Status: inactive and masked.

Remediation

Command Line

Run one of the following commands to either remove ufw or stop and mask ufw:

Run the following command to remove ufw:

apt purge ufw

-OR-

Run the following commands to disable ufw:

ufw disable
systemctl stop ufw
systemctl mask ufw

Default Value

ufw is installed and enabled by default.

References

  1. NIST SP 800-53 Rev. 5: CA-9, SC-7
  2. CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0

CIS Controls

Version 8

4.4 Implement and Manage a Firewall on Servers - Implement and manage a firewall on servers, where supported.

4.5 Implement and Manage a Firewall on End-User Devices - Implement and manage a host-based firewall or port-filtering tool on end-user devices.

Version 7

9.4 Apply Host-based Firewalls or Port Filtering - Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed.

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

Assessment Status

Automated