SSH brute forcing is automated password guessing against Secure Shell (SSH) services. Attackers try large lists of usernames and passwords, or common defaults, until one login works or the service rate-limits, blocks, or locks the account. It is effective when internet-facing devices expose SSH and rely on weak, reused, or factory-set credentials.
In cyber security, this matters because SSH often provides direct administrative access to routers, cameras, servers, and edge appliances. A successful guess can give an attacker full control, enabling malware installation, lateral movement, or use of the device as a bot or proxy node. Defenders reduce the risk by disabling SSH where it is not needed, restricting access with firewalls or VPNs, enforcing unique strong passwords or key-based authentication, and monitoring for repeated failed logins, unusual source IPs, and bursts of authentication attempts.