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Nmap, short for Network Mapper, is a free and open-source utility designed for network exploration and security auditing.
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Originally developed by Gordon Lyon (also known by his pseudonym Fyodor Vaskovich) in 1997, Nmap is used to discover hosts and services on a computer network by sending packets and analyzing the responses.
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It is widely used by network administrators, security professionals, and penetration testers for tasks such as network inventory, managing service upgrade schedules, monitoring host or service uptime, and identifying potential vulnerabilities.
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Nmap operates by using raw IP packets in novel ways to determine what hosts are available on a network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, and what type of packet filters or firewalls are in use.
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It supports various scanning techniques, including TCP SYN scans (stealth scans), TCP connect scans, UDP scans, ping sweeps, and more.
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These methods allow Nmap to classify ports as open, closed, filtered, or unfiltered based on the responses received.
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Key features of Nmap include host discovery, port scanning, service version detection, operating system fingerprinting, and scriptable interaction via the Nmap Scripting Engine (NSE), which enables automated vulnerability detection and advanced service analysis.
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Nmap can also detect reverse DNS names, device types, and MAC addresses, and it supports multiple output formats such as text, XML, grepable, and interactive.
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While Nmap is commonly used for ethical purposes like security assessments and network management, it can also be exploited by threat actors for reconnaissance.
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Its versatility and power have made it a foundational tool in cybersecurity, frequently cited in academic and professional contexts.
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Nmap runs on all major operating systems, including Linux, Windows, macOS, and others, and is available in both command-line and graphical interfaces like Zenmap.
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Due to its potential for misuse, responsible use with proper authorization is essential, as unauthorized scanning may be disruptive or illegal in certain jurisdictions.
