Linuxfocus.org: Learning with nmap Posted August 13, 2001 by Linux-2000 Staff

By Danilo lujambio Abstract:

Why are scanners so important for the security of networks? Basically because they are essential tools for those who want to attack a system. The preparation of an attack by a cracker could look as follows:

Scan a target machine or selected network, observe which services are offered and which operating systems runs these services, and work on some well-known vulnerability in any of them. Scan any network or machine, look for a service or operating system (including the checkup of the version) with a known vulnerability.

For a system administrator who is aware of system security, it is important to carry out a scanning of their own network, and look for vulnerabilities before others do it with not so good intentions.

There are several scanning tools for this purpose, but the article will only look at nmap. Nmap is among the most complete scanners and security tools.

Nmap allows the system administrator to scan the networks in order to know which servers are active and which services they offer. For this purpose, nmap offers several scanning techniques. This article will work on a limited number of them, reviewing (maybe teaching?) some aspects of TCP protocol.

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