# Cis Ubuntu1804 V220 6 2 8

> Ensure no duplicate group names exist

- Skill: `cyberstrikeus/cis-ubuntu1804-v220-6-2-8` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-6-2-8`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-6-2-8/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-v220-6-2-8

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# 6.2.8 Ensure no duplicate group names exist (Automated)

## Profile

- Level 1 - Server
- Level 1 - Workstation

## Description

Although the `groupadd` program will not let you create a duplicate group name, it is possible for an administrator to manually edit the `/etc/group` file and change the group name.

## Rationale

If a group is assigned a duplicate group name, it will create and have access to files with the first GID for that group in `/etc/group`. Effectively, the GID is shared, which is a security problem.

## Audit Procedure

### Command Line

Run the following script and verify no results are returned:

```bash
#!/usr/bin/env bash

{
    while read -r l_count l_group; do
        if [ "$l_count" -gt 1 ]; then
            echo -e "Duplicate Group: \"$l_group\" Groups: \"$(awk -F: '($1 == n) { print $1 }' n=$l_group /etc/group | xargs)\""
        fi
    done < <(cut -f1 -d":" /etc/group | sort -n | uniq -c)
}
```

## Expected Result

No output should be returned.

## Remediation

### Command Line

Based on the results of the audit script, establish unique names for the user groups. File group ownerships will automatically reflect the change as long as the groups have unique GIDs.

## References

1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5

## CIS Controls

- v8: **5.2** Use Unique Passwords
- v7: **4.4** Use Unique Passwords