Mitigate Linux security risks at System & Application Level

Hardening techniques should include following measures:

Users, Groups, and Permissions
ACL and File Permissions
Directory Permissions
The Sticky Bit
SetUID and SetGID
Security at Kernel Space
Web Application (e.g.: Apache Webserver)
Chroot Jail
Patch Management
Network-Level Access Controls (e.g. by IPtables or Firewalld)
SELinux
Logging and syslog
Encryption schemes for logging