Introduction to Nmap and Network Scanning
What is Nmap?
Nmap (Network Mapper) is a powerful open-source tool used for network discovery and security auditing. It is designed to efficiently scan networks and hosts, providing valuable information about their status, services, and potential vulnerabilities.
Network Scanning Basics
Network scanning is the process of identifying active hosts, open ports, and running services on a network. Nmap offers a wide range of scanning techniques, including:
- TCP connect scans
- SYN scans
- UDP scans
- Idle/zombie scans
- Stealth scans
Nmap Scan Types
Nmap supports various scan types, each with its own advantages and use cases:
- TCP SYN Scan
- TCP Connect Scan
- UDP Scan
- TCP Null Scan
- TCP FIN Scan
- TCP Xmas Scan
Nmap Scan Modifiers
Nmap provides numerous scan modifiers that allow you to customize your scans, such as:
-sV
: Probe open ports to determine service/version info
-sC
: Use default nmap scripts for further enumeration
-sU
: UDP scan
-sS
: TCP SYN scan (default if not root)
-sT
: TCP connect scan (default for non-root users)
-p-
: Scan all ports instead of just the most common 1000
Nmap Output and Reporting
Nmap generates detailed output that includes information about the scanned hosts, open ports, running services, and potential vulnerabilities. The output can be saved in various formats, such as XML, greppable, and normal.