Cis Ubuntu1604 V200 5 3 8

---
name: cis-ubuntu1604-v200-5-3-8
description: "Ensure SSH MaxAuthTries is set to 4 or less"
category: cis-networking
version: "2.0.0"
author: cyberstrike-official
tags: [cis, ubuntu, linux, ubuntu-16.04, ssh, remote-access]
cis_id: "5.3.8"
cis_benchmark: "CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0"
tech_stack: [ubuntu, linux]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.8

## Description

The `MaxAuthTries` parameter specifies the maximum number of authentication attempts permitted per connection. When the login failure count reaches half the number, error messages will be written to the `syslog` file detailing the login failure.

## Rationale

Setting the `MaxAuthTries` parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. While the recommended setting is 4, set the number based on site policy.

## Audit Procedure

### Command Line

Run the following command and verify that output `MaxAuthTries` is 4 or less:

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

### Expected Result

```
maxauthtries 4
```

Run the following command and verify that the output:

```bash
grep -Ei '^\s*maxauthtries\s+([5-9]|[1-9][0-9]+)' /etc/ssh/sshd_config
```

Nothing is returned.

## Remediation

### Command Line

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

```
MaxAuthTries 4
```

## Default Value

MaxAuthTries 6

## References

1. SSHD_CONFIG(5)

## CIS Controls

Version 7

16.13 Alert on Account Login Behavior Deviation - Alert when users deviate from normal login behavior, such as time-of-day, workstation location and duration.

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Assessment Status

Automated