Network Mapping with Nmap: The Basics of Reconnaissance in Network Security

In the world of cybersecurity, understanding how a network is structured is a crucial first step. This process is known as network mapping, a technique for identifying hosts, services, ports, and operating systems running on a network. One of the most popular and powerful tools for network mapping is Nmap (Network Mapper).

What is Network Mapping?

Network mapping is the process of identifying and understanding the structure of a network. Through this technique, we can identify active hosts, open ports, running services, and the operating system used by the target. In some cases, network mapping is also used to obtain a general overview of the network topology.

How Does Network Mapping Work?

Technically, network mapping is performed by sending specific packets to a target network and then analyzing the received responses. When a host replies to an ICMP Echo Request, it indicates that the host is active. If a TCP port responds with a SYN-ACK, it can be assumed to be open. Conversely, when no response is received, the port is likely closed or its traffic is being filtered by a firewall. This process can be done manually, but tools like Nmap automate the entire mechanism through a variety of efficient and flexible scanning techniques.

Introduction to Nmap

Nmap (Network Mapper) is an open-source tool used to:

• Network discovery
• Port scanning
• Service enumeration
• OS detection
• Vulnerability detection (melalui Nmap Scripting Engine)

Nmap is available on various operating systems such as Linux, Windows, and macOS, and is the default tool for network security practitioners.

Basic Nmap Commands and Their Explanations

1. Host Discovery

• -sn → Disable port scan
• Used to determine which hosts are active
• Suitable for the initial stages of network mapping

Nmap -sn (?)

2. Port Scanning
Explanation:

• Scans all 65535 ports
• Used for deep reconnaissance

Nmap -p- (?)

3. TCP Scan Techniques
Explanation:

• Most popular scanning method
• Fast and relatively stealthy
• Requires root/admin privileges

Nmap -sS (?)

TCP Connect Scan
Explanation:

• Uses full TCP handshake
• Used if you don’t have root rights

Nmap -sT (?)

4. Output & Dokumentasi
Explanation:

• Output to format:
  .nmap .xml .gnmap

Nmap -oA network scan (?)

5. Complete Network Mapping
Explanation:
Stage 1: Identify active hosts
Stage 2: Mapping specific target details

Nmap -sS (?) && Nmap -sS -sV -O (?)

Conclusion
Network mapping is the foundation of the entire network security process. By understanding the structure and running services, we can:

• Identify security risks
• Reduce the attack surface
• Perform system hardening appropriately

Nmap is a crucial tool because it is flexible, powerful, and constantly evolving. Mastering basic Nmap commands is a must-have skill for anyone involved in ethical hacking, penetration testing, or network security.

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Source
https://hackertarget.com/nmap-tutorial/
https://medium.com/@maxrooted/tutorial-nmap-bahasa-indonesia-basic-guide-8044739777c2
https://null-byte.wonderhowto.com/how-to/tactical-nmap-for-beginner-network-reconnaissance-0189856/