Hardening aims to reduce the attack surface of IT systems by retaining only the objects and configurations required for the operation of servers, workstations or applications.
Hardening can thus include limiting privileges, restrictions on authorised programs, the disabling of obsolete or unnecessary services and local firewalling, among others.
There are a number of hardening guides providing higher or lower levels of security depending on the applications and standards.
Examples of hardening guides:
Security Technical Implementation Guides
NSA Security Configuration Guidance
ACSC – Hardening Microsoft Windows 10, version 21H1, Workstations