Nmap

Nmap (short for Network Mapper) is a powerful open-source tool used for:

• Port scanning: See which ports are open on a target machine.

• Service detection: Identify what services (e.g., HTTP, SSH) are running and their versions.

• OS fingerprinting: Guess the operating system of a remote host.

• Network inventory: Map out devices on a network.

• Vulnerability scanning: With scripts (via Nmap Scripting Engine, NSE), it can detect known vulnerabilities.

​Nmap basic commands:

• -sT TCP Connect: Full connection; easy to detect; no root needed

• -sS SYN (Stealth): Half-open scan; fast and stealthy; needs root.

• -sU UDP Scan: Scans UDP ports; slower and less reliable.

• -sV Version Detection: Identifies service versions.

• -O OS Detection: Guesses operating system via fingerprinting.

• -sn Ping Scan: Checks which hosts are online; no port scan.

• -A Aggressive Scan: Combines OS, version, script, and traceroute.

• --script NSE: Runs custom scripts for advanced scanning.