[ Thanks to Michael Hall for this link. ]
“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…”