# Cis Ubuntu1604 V200 6 2 1

> Ensure accounts in /etc/passwd use shadowed passwords

- Skill: `cyberstrikeus/cis-ubuntu1604-v200-6-2-1` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1604-v200-6-2-1`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1604-v200-6-2-1/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector CAUTION)
- 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-ubuntu1604-v200-6-2-1

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# CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 6.2.1

## Profile

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

## Description

Local accounts can uses shadowed passwords. With shadowed passwords, The passwords are saved in shadow password file, `/etc/shadow`, encrypted by a salted one-way hash. Accounts with a shadowed password have an `x` in the second field in `/etc/passwd`.

## Rationale

The `/etc/passwd` file also contains information like user ID's and group ID's that are used by many system programs. Therefore, the `/etc/passwd` file must remain world readable. In spite of encoding the password with a randomly-generated one-way hash function, an attacker could still break the system if they got access to the `/etc/passwd` file. This can be mitigated by using shadowed passwords, thus moving the passwords in the `/etc/passwd` file to `/etc/shadow`. The `/etc/shadow` file is set so only root will be able to read and write. This helps mitigate the risk of an attacker gaining access to the encoded passwords with which to perform a dictionary attack.

**Notes:**

- All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user.
- A user account with an empty second field in `/etc/passwd` allows the account to be logged into by providing only the username.

## Audit Procedure

### Command Line

Run the following command and verify that no output is returned:

```bash
awk -F: '($2 != "x" ) { print $1 " is not set to shadowed passwords "}' /etc/passwd
```

## Expected Result

No output should be returned.

## Remediation

### Command Line

Run the following command to set accounts to use shadowed passwords:

```bash
sed -e 's/^\([a-zA-Z0-9_]*\):[^:]*:/\1:x:/' -i /etc/passwd
```

Investigate to determine if the account is logged in and what it is being used for, to determine if it needs to be forced off.

## Default Value

N/A

## References

N/A

## CIS Controls

| Controls Version | Control                                                                                                                                                                                               | IG 1 | IG 2 | IG 3 |
| ---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---- | ---- | ---- |
| v7               | 4.4 Use Unique Passwords<br/>Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that system. |      |      |      |