Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including United States Department of Defense–style mandatory access controls (MAC).
Advanced Intrusion Detection Environment (Aide) takes a “snapshot” of the state of the system, register hashes, modification times, and other data regarding the files defined by the administrator. Aide can be configured to run on a schedule and report changes.
The Security Technical Implementation Guides (STIGs) and the NSA Guides are the configuration standards for DOD IA and IA-enabled devices/systems. The STIGs contain technical guidance to “lock down” information systems/software that might otherwise be vulnerable to a malicious computer attack. The STIG compliancy can be determined with the OpenSCAP ecosystem.
The Federal Information Processing Standard (FIPS) Publication 140-2, is a computer security standard, developed by a U.S. Government and industry working group to validate the quality of cryptographic modules. (RedHat).