"nmap is the most powerful, most flexible network exploration tool and security scanner. It's the tool of choice for auditing your network for vulnerabilities. Search for the same weaknesses intruders are looking for. nmap's slogan is 'audit your network before the bad guys do.'
"A more accurate definition of nmap is 'TCP stack analyzer.' nmap builds different types of TCP packets, sends them to the target, then analyzes the responses. It is quite amazing what the author of nmap, Fyodor, has accomplished by studying and analyzing TCP packets, and what different operating systems do to them.
"Because nmap is so good at what it does, it is the tool of choice for evil crackers, which raises some ethical questions: is it OK to portscan other people's networks? It is not an intrusion device. It's more akin to 'casing the joint,' just looking around to see what there is. Not touching, just being nosy..."
