Scanning networks with Nmap

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1. What is Nmap? 🔎

Nmap (Network Mapper) is an open-source tool used for network discovery and security auditing.
It helps identify:

  • Active hosts 🖥️

  • Open ports 🚪

  • Running services ⚙️

  • Operating systems 💻

👉 Commonly used by network administrators and security professionals.

2. Why Use Nmap? 🎯

  • Discover devices on a network 🌐

  • Identify open ports & services 🚪

  • Detect vulnerabilities ⚠️

  • Perform security assessments 🛡️

  • Troubleshoot network issues 🔧

3. Basic Nmap Syntax 🖥️

nmap [scan type] [options] target

Example:

nmap 192.168.1.1

This scans a single host for open ports.

4. Common Nmap Scan Types 🧪

1. Ping Scan (Host Discovery) 🏓

nmap -sn 192.168.1.0/24

  • Finds active devices in a network

  • Does NOT scan ports

2. TCP Connect Scan 🔗

nmap -sT target

  • Full TCP connection

  • Easy to detect

3. SYN Scan (Stealth Scan) 🕵️

nmap -sS target

  • Half-open scan

  • Faster and stealthier

4. Service Version Detection 🔍

nmap -sV target

  • Detects running service versions

5. OS Detection 💻

nmap -O target

  • Attempts to identify operating system

6. Aggressive Scan 🚀

nmap -A target

  • Enables OS detection

  • Version detection

  • Script scanning

  • Traceroute

5. Port Scanning Options 🚪

  • Scan specific port:

nmap -p 80 target

  • Scan multiple ports:

nmap -p 22,80,443 target

  • Scan all ports:

nmap -p- target

6. Output Options 📄

  • Save output to file:

nmap -oN output.txt target

Useful for reporting and documentation 📊

7. Best Practices ⚠️

✅ Always get permission before scanning
✅ Use Nmap in lab or authorized environments only
✅ Avoid aggressive scans on production networks
✅ Analyze results carefully before making conclusions

⚖️ Unauthorized scanning can be illegal.

8. Quick Summary 🧠

Nmap helps you:

  • Discover hosts 🖥️

  • Identify open ports 🚪

  • Detect services & OS 💻

  • Perform security audits 🛡️

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