Essential Nmap Commands for CEH, HTB, and TryHackMe

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Nmap (Network Mapper) is an essential tool in every security professional’s toolkit. Here’s my personal collection of frequently used Nmap commands, especially useful for CEH certification, HackTheBox, and TryHackMe challenges.

Host Discovery

Before diving into detailed scans, it’s crucial to identify active hosts in your target network:

# Scan for alive hosts (no port scan)
nmap -sn $ip/24

# Faster host scan with no DNS resolution
nmap -sn -n $ip/24 > ip-range.txt

# Scan specific IP range
nmap -sP 10.0.0.0-100

Tip: Use these commands to identify which hosts are up before diving into detailed port or vulnerability scans.

Basic Scans

These are your bread-and-butter Nmap commands for initial reconnaissance:

# Basic scan of 1000 common ports
nmap [target]

# Scan all TCP ports (65535)
nmap -p- [target]

# Quick UDP scan
nmap -sU [target]

# Version & OS detection
nmap -sC -sV -O -oA initial [target]

# Fast scan of 100 common ports
nmap -F [target]

Service & Vulnerability Enumeration

Deeper inspection of services and potential vulnerabilities:

# Default script scan & version detection
nmap -sC -sV -oN scan.txt [target]

# Scan for vulnerabilities
nmap --script vuln [target]

# Use multiple script categories
nmap --script vuln,safe,discovery -oN scan.txt [target]

Tip: Running service detection (-sV) and using scripts can give you insights into what versions are running and potential vulnerabilities, helping you prioritize further actions.

Specific Port Scans

Target specific ports or ranges:

# TCP scan of specific ports
nmap -p T:80,443,8080 [target]

# Full connect scan on all ports
nmap -v -p- -sT [target]

# Scan specific port range with no retries
nmap -p 21-25 [target] --max-retries 0

Aggressive & Full Scans

When you need comprehensive results:

# Aggressive scan (faster)
nmap -T4 [target]

# Full TCP scan with scripts and version detection
nmap -sC -sV -p- -v -T4 -oN full.txt [target]

# Full UDP scan
nmap -sU -O -p- -T4 -oN nmap/udp.txt [target]

# Max scan delay control
nmap -sC -sV [target] -v --max-scan-delay=10

Tip: Aggressive timing templates like -T4 speed up scans but can be more detectable. Consider using stealthier options if you want to avoid detection.

Advanced Techniques

For more sophisticated scanning needs:

# Deep scanning - all ports with full connect
nmap -v -p- -sT $ip

# TCP SYN scan (stealthy)
nmap -sS [target]

# TCP ACK scan
nmap -sA [target]

# Top ports scan
nmap --top-ports=20 [target]

Port Knocking

Sometimes services are hidden behind port knock sequences:

# Port knock with retries
for x in 7000 8000 9000; do
    nmap -Pn --host_timeout 201 --max-retries 0 -p $x $ip
done

Useful Automation Tools

Several tools can help automate and enhance your Nmap scans:

1. AutoRecon: A multi-threaded network reconnaissance tool

   • GitHub: AutoRecon

2. Onetwopunch: Combines unicornscan and Nmap for efficient scanning

   • GitHub: onetwopunch

3. nmapAutomator: Automates the Nmap scanning process

   • GitHub: nmapAutomator

Best Practices

1. Start Broad, Then Focus: Begin with host discovery and basic scans before diving into detailed port scans
2. Consider the Network: Use appropriate timing templates based on network stability
3. Save Your Output: Always use output options (-oN, -oX) for later reference
4. Be Mindful of Noise: More aggressive scans are noisier and more detectable

Further Reading

For more advanced techniques on evading firewalls with Nmap, check out my detailed blog post on Firewalls Evading Techniques in Nmap.

Remember, with great power comes great responsibility. Always ensure you have proper authorization before scanning any networks or systems.