Sometimes you need speed, other times you may need stealth. In some cases,
bypassing firewalls may be required. Not to mention the fact that you may
want to scan different protocols (UDP, TCP, ICMP, etc.).
You just can't do all this with one scanning mode. Thus nmap
incorporats virtually every scanning technique known of.
See the nmap homepage at http://www.insecure.org/nmap/index.html
