SSH Brute Force

Failed Password for Invalid User? (SSH Attack Explained + Fix)

Seeing 'Failed password for invalid user' in your SSH logs? Learn what it means, if you're under attack, and how to stop brute-force attempts.

Signature Log Pattern

server.log
Failed password for invalid user admin from 185.234.217.22 port 54432 ssh2

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What Is a SSH Brute Force?

This log entry indicates that someone attempted to log into your server using SSH with a username that does not exist. Attackers commonly use automated scripts to try thousands of username and password combinations across exposed servers.

The presence of repeated entries like this usually means your server is being targeted in a brute-force attack. While a single attempt is harmless, continuous attempts from multiple IP addresses indicate coordinated scanning activity.

If left unprotected, attackers may eventually guess weak credentials or exploit misconfigurations, gaining unauthorized access to your system.

How to Defend Against This Threat

  • Disable password authentication and use SSH key-based login only.

  • Change the default SSH port from 22 to a non-standard port.

  • Install Fail2Ban or similar tools to block repeated login attempts.

  • Restrict SSH access to specific IP addresses using a firewall.

  • Use strong, unique usernames instead of common ones like 'admin' or 'root'.

Related Threats

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