What is SSHGuard?

SSHGuard is an open source intrusion prevention software designed to protect Linux and BSD based systems that run SSH servers. It analyzes system log files in real-time to detect attacks such as brute force attempts to guess passwords, scans searching for SSH server vulnerabilities, and other common attacks targeting systems with SSH ports exposed to the internet.

SSHGuard works by leveraging the power of IPtables firewall rules on Linux and PF firewall on BSD systems. When an attack is detected via the logs, SSHGuard will immediately block the attacker's IP address automatically at the firewall level. The ban can be configured to expire after a set amount of time or stay permanently blocked depending on preferences.

Some key capabilities and benefits of SSHGuard include:

• Lightweight software with minimal system resource usage
• Easy installation and configuration, no need to modify SSH server configs
• Real-time attack detection by parsing auth and firewall logs
• Automatic blocking at firewall level when attacks are seen
• Predefined ban thresholds for common vectors like SSH brute force
• Configurable ban duration, from temporary to permanent blocking
• Whitelist to exclude trusted IP ranges from ever being blocked

Overall, SSHGuard serves as an integral layer of defense to significantly enhance the security of SSH server environments. It prevents attackers from completing brute force and scanning attacks, stopping threats at the network perimeter while requiring minimal setup and ongoing management.

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