nmap is a powerful network scanning tool used to discover hosts and services on a computer network by sending packets and analyzing the responses. It's widely used for network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Basic Port Scan
Example Usage:
nmap 192.168.1.1
What it does:
Scans the specified IP address (192.168.1.1) for open TCP ports. It uses a default scan, typically a TCP connect scan.
Command-line Arguments Explained:
- 192.168.1.1: Specifies the target IP address to scan.
Scan a Range of IPs
Example Usage:
nmap 192.168.1.1-254
What it does:
Scans a range of IP addresses from 192.168.1.1 to 192.168.1.254.
Command-line Arguments Explained:
- 192.168.1.1-254: Specifies the IP address range to scan.
Scan a Network
Example Usage:
nmap 192.168.1.0/24
What it does:
Scans the entire /24 network (192.168.1.0 to 192.168.1.255).
Command-line Arguments Explained:
- 192.168.1.0/24: Specifies the network to scan using CIDR notation.
Scan for Specific Ports
Example Usage:
nmap -p 80,443 192.168.1.1
What it does:
Scans the specified IP address (192.168.1.1) for ports 80 and 443 only.
Command-line Arguments Explained:
- -p: Specifies the ports to scan.
- 80,443: Lists the ports to be scanned, separated by commas.
- 192.168.1.1: Specifies the target IP address to scan.
TCP Connect Scan
Example Usage:
nmap -sT 192.168.1.1
What it does:
Performs a TCP connect scan, which establishes a full TCP connection to each port. This is the most reliable scan type but is often detected and logged.
Command-line Arguments Explained:
- -sT: Specifies a TCP connect scan.
- 192.168.1.1: Specifies the target IP address to scan.
TCP SYN Scan (Stealth Scan)
Example Usage:
nmap -sS 192.168.1.1
What it does:
Performs a TCP SYN scan (also known as a "stealth scan"), which sends a SYN packet and waits for a SYN/ACK (port open) or RST (port closed) response, but does not complete the three-way handshake, making it less likely to be logged. Requires root privileges.
Command-line Arguments Explained:
- -sS: Specifies a TCP SYN scan.
- 192.168.1.1: Specifies the target IP address to scan.
UDP Scan
Example Usage:
nmap -sU 192.168.1.1
What it does:
Performs a UDP scan, which sends UDP packets to target ports. UDP scans are slower than TCP scans.
Command-line Arguments Explained:
- -sU: Specifies a UDP scan.
- 192.168.1.1: Specifies the target IP address to scan.
Ping Scan (Host Discovery)
Example Usage:
nmap -sn 192.168.1.0/24
What it does:
Performs a ping scan to discover live hosts on the network without performing a port scan. This is useful for quickly identifying active hosts.
Command-line Arguments Explained:
- -sn: Specifies a ping scan (host discovery).
- 192.168.1.0/24: Specifies the network to scan.
Aggressive Scan
Example Usage:
nmap -A 192.168.1.1
What it does:
Performs an aggressive scan, which includes OS detection (-O), version detection (-sV), script scanning (-sC), and traceroute.
Command-line Arguments Explained:
- -A: Enables aggressive scanning.
- 192.168.1.1: Specifies the target IP address to scan.
OS Detection
Example Usage:
nmap -O 192.168.1.1
What it does:
Attempts to determine the operating system of the target host.
Command-line Arguments Explained:
- -O: Enables OS detection.
- 192.168.1.1: Specifies the target IP address to scan.
Version Detection
Example Usage:
nmap -sV 192.168.1.1
What it does:
Attempts to determine the version of services running on open ports.
Command-line Arguments Explained:
- -sV: Enables version detection.
- 192.168.1.1: Specifies the target IP address to scan.
Script Scan
Example Usage:
nmap --script=vuln 192.168.1.1
What it does:
Runs a script scan using the Nmap Scripting Engine (NSE) to detect vulnerabilities or perform other tasks. This example uses the 'vuln' script to detect known vulnerabilities.
Command-line Arguments Explained:
- --script=vuln: Specifies the script or script category to use. 'vuln' is a common script category.
- 192.168.1.1: Specifies the target IP address to scan.
Output to File
Example Usage:
nmap -oN output.txt 192.168.1.1
What it does:
Saves the scan results in a normal text format to the specified file (output.txt).
Command-line Arguments Explained:
- -oN: Specifies the output file and format (normal).
- output.txt: The name of the file to save the output to.
- 192.168.1.1: Specifies the target IP address to scan.
Example Usage:
nmap -oX output.xml 192.168.1.1
What it does:
Saves the scan results in XML format to the specified file (output.xml).
Command-line Arguments Explained:
- -oX: Specifies the output file and format (XML).
- output.xml: The name of the file to save the output to.
- 192.168.1.1: Specifies the target IP address to scan.
Fast Scan
Example Usage:
nmap -F 192.168.1.1
What it does:
Performs a fast scan, which scans fewer ports than the default scan, making it quicker.
Command-line Arguments Explained:
- -F: Specifies a fast scan.
- 192.168.1.1: Specifies the target IP address to scan.
