SSH Security
SSH (Secure Shell) security encompasses the configurations, practices, and controls used to protect the SSH protocol, which provides encrypted remote access and file transfer capabilities, from unauthorized access and exploitation.
SSH is the standard protocol for secure remote administration of servers and network devices, replacing insecure alternatives like Telnet and rlogin. It provides encrypted communication, authentication, and data integrity. However, improper SSH configuration can introduce significant security vulnerabilities that attackers actively exploit.
Common SSH security risks include brute force attacks against password authentication, use of weak or deprecated cryptographic algorithms, exposure of SSH services to the entire internet, misconfigured key permissions, and private key theft. Attackers who compromise SSH credentials gain direct command-line access to systems, making SSH a high-value target.
Best practices for SSH security include disabling password authentication in favor of key-based authentication, using strong key types like Ed25519 or RSA with at least 4096-bit keys, disabling root login, changing the default port to reduce automated scanning noise, implementing fail2ban or similar tools to block brute force attempts, restricting SSH access to specific IP ranges through firewall rules, enabling two-factor authentication, keeping SSH software updated, and auditing authorized keys files regularly. SSH certificate-based authentication provides scalable key management for larger environments.