# Cis Ubuntu1604 V200 5 3 4

> Ensure SSH Protocol is set to 2

- Skill: `cyberstrikeus/cis-ubuntu1604-v200-5-3-4` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1604-v200-5-3-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1604-v200-5-3-4/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-ubuntu1604-v200-5-3-4

---


# CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.4

## Description

SSH supports two different and incompatible protocols: SSH1 and SSH2. SSH1 was the original protocol and was subject to security issues. SSH2 is more advanced and secure.

## Rationale

SSH v1 suffers from insecurities that do not affect SSH v2.

## Audit Procedure

### Command Line

Run the following command and verify that output matches:

```bash
sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep '^\s*protocol'
```

### Expected Result

```
protocol 2
```

Run the following command and verify the output:

```bash
grep -Ei '^\s*Protocol\s+[^2].*$' /etc/ssh/sshd_config
```

Nothing should be returned.

## Remediation

### Command Line

Edit the `/etc/ssh/sshd_config` file to set the parameter as follows:

```
Protocol 2
```

## Default Value

Protocol 2

## References

1. SSHD_CONFIG(5)

## CIS Controls

Version 7

9.2 Ensure Only Approved Ports, Protocols and Services Are Running - Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Assessment Status

Automated