Study of nmap Command

 

Experiment

Study of nmap Command

🎯 Aim

To explore and analyze network hosts and services using the nmap command.

---

📘 Objective

By the end of this experiment, students will be able to:

• Discover active hosts in a network
• Scan open ports
• Identify running services
• Understand basic network security scanning

---

📖 Theory

The nmap (Network Mapper) command is a powerful tool used for:

• Network discovery
• Security auditing
• Port scanning

👉 It works by sending packets to target systems and analyzing responses.

👉 It can detect:

• Open ports
• Closed ports
• Filtered ports (blocked by firewall)

---

🧾 Syntax

nmap [options] <target>

• <target> → IP address, hostname, or network range

---

🔧 Common Options

• -sS → TCP SYN scan (stealth scan)
• -sT → TCP connect scan
• -sU → UDP scan
• -p → Specify port(s)
• -A → Aggressive scan (OS + version detection)
• -O → OS detection
• -v → Verbose output
• -F → Fast scan (common ports only)

---

🧰 Prerequisites

• Linux system
• Root/sudo privileges (for advanced scans)
• nmap installed

Installation:

sudo apt install nmap

---

🔬 Procedure & Commands

1️⃣ Scan a Single Host

nmap 192.168.1.1

---

2️⃣ Scan a Domain

nmap google.com

---

3️⃣ Scan Specific Ports

nmap -p 22,80,443 192.168.1.1

---

4️⃣ Scan a Range of IPs

nmap 192.168.1.1-100

---

5️⃣ Perform Stealth Scan

sudo nmap -sS 192.168.1.1

---

6️⃣ Detect OS and Services

sudo nmap -A 192.168.1.1

---

7️⃣ Fast Scan

nmap -F 192.168.1.1

---

🖥️ Sample Output

PORT        STATE      SERVICE
22/tcp      open       ssh
80/tcp      open       http
443/tcp     open       https

---

🔍 Output Interpretation

Field	Meaning
PORT	Port number and protocol
STATE	open / closed / filtered
SERVICE	Service running on the port

---

🔑 Port States

• Open → Service is running
• Closed → No service running
• Filtered → Blocked by firewall

---

📝 Exercises for Students

1. Scan your local system (localhost).
2. Identify open ports on a given IP.
3. Perform a fast scan and compare with normal scan.
4. Scan a network range and list active hosts.
5. Analyze differences between TCP and UDP scans.

---

❓ Viva Questions

• What is nmap used for?
• What is port scanning?
• Difference between open and filtered ports?
• What is a stealth scan?
• Why is nmap important in security?

---

⚠️ Precautions

• ⚠️ Scan only authorized systems (important ethical rule)
• Requires root privileges for advanced scans
• Can be detected by firewalls/IDS

---

✅ Result

The nmap command is a powerful tool for network exploration and security auditing, widely used by network administrators and cybersecurity professionals.