This document provides an overview of security tools and concepts for Linux systems. It discusses Linux file structure, basic commands, vulnerabilities, compiling programs, security tools like Nmap, Nessus, SARA, iptables firewall, password cracking with John the Ripper, intrusion detection with Snort, network monitoring tools like tcpdump, and security hardening techniques like chrooting. The document aims to familiarize the reader with fundamental Linux security topics.