# Cis GCP Cos 5.1.9

> Ensure SSH HostbasedAuthentication is disabled

- Skill: `cyberstrikeus/cis-gcp-cos-5-1-9` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-gcp-cos-5-1-9`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-gcp-cos-5-1-9/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-gcp-cos-5-1-9

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# 5.1.9 Ensure SSH HostbasedAuthentication is disabled (Automated)

## Description

The `HostbasedAuthentication` parameter specifies if authentication is allowed through trusted hosts via the user of `.rhosts`, or `/etc/hosts.equiv`, along with successful public key client host authentication. This option only applies to SSH Protocol Version 2.

## Rationale

Even though the `.rhosts` files are ineffective if support is disabled in `/etc/pam.conf`, disabling the ability to use `.rhosts` files in SSH provides an additional layer of protection.

## Audit Procedure

Run the following command and verify that output matches:

```bash
# sshd -T | grep hostbasedauthentication

HostbasedAuthentication no
```

## Expected Result

Output should show `HostbasedAuthentication no`.

## Remediation

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

```
HostbasedAuthentication no
```

## Default Value

HostbasedAuthentication no

## CIS Controls

| Controls Version | Control                                             | IG 1 | IG 2 | IG 3 |
| ---------------- | --------------------------------------------------- | ---- | ---- | ---- |
| v8               | 6.3 Require MFA for Externally-Exposed Applications |      | x    | x    |
| v7               | 16.3 Require Multi-factor Authentication            |      | x    | x    |

## Profile

- Level 1 - Server