What is NMAP?

Nmap, or "Network Mapper," is a free and open-source network scanning utility used for security auditing and network exploration.

It was created to help network administrators discover active hosts, open ports, running services, and potential vulnerabilities on their networks. 

How Nmap works

Nmap operates by sending specially crafted raw IP packets to a target network or host and then analyzes the responses to gather information. Some of the techniques it uses to gather data include: 

•   Host discovery: Determines which hosts on a specified network are online and responsive.
• Port scanning: Detects open ports and classifies them as open, closed, or filtered.
• OS fingerprinting: Identifies the operating system running on a remote host.
• Version detection: Determines the service name and version number for applications running on open ports.
• Nmap Scripting Engine (NSE): Allows users to write scripts in Lua to automate scanning tasks and perform more advanced tasks like vulnerability detection and exploitation.
• Common uses for Nmap
• Security auditing: Cybersecurity professionals use Nmap to scan networks for weaknesses, ensuring that security policies are followed and no unauthorized devices are connected.
• Penetration testing: Ethical hackers use Nmap to map out a network's attack surface and identify potential entry points before simulating an attack.
• Network inventory and monitoring: Network administrators use Nmap to discover all devices on their network and monitor them for any changes.
• Troubleshooting: Nmap can help identify the root cause of network issues by determining the status of network services and devices. 

Key features

• Cross-platform compatibility: Nmap runs on most major operating systems, including Linux, Windows, and macOS.
• Flexibility: Nmap offers dozens of advanced techniques for navigating networks with firewalls and other obstacles.
• Output formats: Results can be saved in various formats, such as text, XML, and greppable output, for further analysis and reporting.
• Graphical user interface (GUI): Zenmap is a graphical version of Nmap that provides an easy-to-use interface for beginners. 
• Note: Always ensure you have proper authorization before scanning any network, especially outside of your own. Unauthorized scanning may be illegal.