System Hardening is a process to secure a computer system. The objective of system hardening is to reduce the security risk by eliminating potential attack vectors (BeyondTrust, 2014). This can be done with a collection of tools, techniques and best practices.
Server hardening involves securing the hardware and software components of a server to protect it from attacks, ensuring that it runs efficiently and securely. This including disable unnecessary services, patch management, SSH security, firewall configuration, etc.
Software application Hardening refers to securing the software applications themselves to prevent vulnerabilities in code or configuration from being exploited by attackers. This including input validation, regular code reviews and testing, encryption and hashing, logging and monitoring, etc.
Operating system hardening focuses on securing the underlying OS (Windows, Linux, etc.) to protect the entire environment from attacks. This including disable unnecessary services and ports, patch and update management, security configurations, auditing and logging, encryption, etc.
Network hardening focuses on securing the communication pathways between systems to ensure safe data transmission and reduce the risk of network-based attacks. This including firewall rules, IDS/IPS, secure protocols, VPN, VLANs and segmentation, etc.