# Warning message when you try to connect to a server using SSH

> Find out why SSH warns that a server's host key has changed and how to clear the old key and connect safely.

Source: https://helpcenter.ruachost.com/getting-started/your-account/warning-message-when-you-try-to-connect-to-a-server-using-ssh/

When connecting to your Ruachost server using SSH, you may sometimes see a warning message about the server’s host key. This article explains why this happens, what it means, and how to resolve it safely.

## The Problem

When you attempt to connect to your server via SSH, you may see a warning message such as:

On **macOS/Linux**:

```
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!         @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
```

```
```

On **Windows (PuTTY)**:

```
WARNING - POTENTIAL SECURITY BREACH!
The server's host key does not match the one PuTTY has cached.
```

This means the server’s RSA fingerprint has changed compared to what your computer has stored.

## Cause

The most common reason is that the server’s SSH host key has legitimately changed — for example, after:

- A server rebuild or OS reinstall
- A new operating system template being applied
- A server migration

However, in rare cases, it could indicate a **man-in-the-middle attack**, where someone is impersonating your server to intercept your connection.

## Resolution

### On macOS and Linux

1. Review the warning message carefully.
2. Note the line that says something like:

   ```
   Offending RSA key in /path/.ssh/known_hosts:x
   ```
3. Open the `known_hosts` file in a text editor:

   ```
   nano /path/.ssh/known_hosts
   ```
4. Delete the line indicated by the warning (line `x`).
5. Save and exit the editor.
6. Reconnect to the server, you will be prompted to accept the new host key.

### On Windows (PuTTY)

When PuTTY shows the warning, you have three options:

- **Yes** – If you know the server was recently reinstalled or updated, click **Yes** to update PuTTY’s cache with the new key.
- **No** – If you’re unsure, click **No** to connect without saving the new key. The warning will appear again next time.
- **Cancel** – If you suspect something malicious, click **Cancel** and do not proceed.

## Important Security Note

- If you **did not** recently reinstall or change your server, and you see this warning, it may indicate a security risk.
- In that case, do **not** proceed with the connection.
- Instead, open a **[support ticke](https://dashboard.ruachost.com/submitticket.php?step=2&deptid=3)t** in your Ruachost Hosting Panel so our team can investigate.