# Cis Ubuntu1804 V220 4 4 4

> Ensure strong password hashing algorithm is configured

- Skill: `cyberstrikeus/cis-ubuntu1804-v220-4-4-4` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-4-4-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-4-4-4/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-ubuntu1804-v220-4-4-4

---


# CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.4.4

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

The commands below change password encryption from md5 to yescrypt (a much stronger hashing algorithm). All existing accounts will need to perform a password change to upgrade the stored hashes to the new algorithm.

## Rationale

The yescrypt algorithm provides much stronger hashing than MD5, which provides protection of the password file even in the event of a system compromise. Note: these changes only apply to accounts configured on the local system.

## Audit Procedure

### Command Line

Run the following command to verify the password hashing algorithm is configured:

```bash
grep -Pi '^\h*password\h+(\S+\h+)+pam_unix\.so\h+([^#\n\r]+\h+)?(sha512|yescrypt)\b' /etc/pam.d/common-password
```

### Expected Result

Output should include `sha512` or `yescrypt`.

Also verify login.defs:

```bash
grep -Pi '^\h*ENCRYPT_METHOD\h+(SHA512|yescrypt)\b' /etc/login.defs
```

## Remediation

### Command Line

Edit `/etc/pam.d/common-password` to include `sha512` or `yescrypt` option to the `pam_unix.so` line:

```
password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt
```

Edit `/etc/login.defs` to set:

```
ENCRYPT_METHOD yescrypt
```

## Default Value

ENCRYPT_METHOD SHA512 (in /etc/login.defs)

## References

1. NIST SP 800-53 Rev. 5: IA-5(1)

## CIS Controls

v8 - 3.11 Encrypt Sensitive Data at Rest - Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data.

v7 - 16.4 Encrypt or Hash All Authentication Credentials.

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Assessment Status

Automated