Introduction to Nmap#

What is Nmap?#

• Open-source network scanning and security auditing tool.
• Written in C, C++, Python, and Lua.
• Scans networks using raw packets.
• Detects:
  • Live hosts on the network
  • Running services and their versions
  • Operating systems and their versions
  • Firewall, IDS, and packet filter configurations

Key Use Cases#

Nmap is widely used by network admins and security experts for:

• 🔐 Security auditing of networks
• 🎯 Simulated penetration testing
• 🧱 Firewall/IDS settings check
• 🗺️ Network mapping
• 🔍 Response and behavior analysis
• 🛑 Open port identification
• ⚠️ Vulnerability assessment

Nmap Architecture#

1. Host Discovery

• Finds which devices are active on a network.

1. Port Scanning

• Identifies open, closed, or filtered ports on a target.

1. Service Enumeration & Detection

• Detects the services running on open ports.
• Also finds the name and version of the application.

1. OS Detection

• Identifies the operating system and version of the host.

1. Nmap Scripting Engine (NSE)

• Allows custom scripts for advanced scanning and exploitation.
• Useful for:
  • Vulnerability detection
  • Backdoor detection
  • Brute-forcing, etc.

Scan Techniques#

performing nmap —help gives us a

nmap --help

Nmap TCP-SYN Scan (-sS) – Simple Note.#

• Also called half-open scan.
• Default scan type in Nmap.
• Very fast and stealthy.
• Does not complete the full 3-way TCP handshake.