Nmap is designed to allow system administrators and curious individuals
to scan large networks to determine which hosts are up and what ser-
vices they are offering. nmap supports a large number of scanning
techniques such as: UDP, TCP connect(), TCP SYN (half open), ftp proxy
(bounce attack), Reverse-ident, ICMP (ping sweep), FIN, ACK sweep, Xmas
Tree, SYN sweep, IP Protocol, and Null scan. See the Scan Types sec-
tion for more details. nmap also offers a number of advanced features
such as remote OS detection via TCP/IP fingerprinting, stealth scan-
ning, dynamic delay and retransmission calculations, parallel scanning,
detection of down hosts via parallel pings, decoy scanning, port fil-
tering detection, direct (non-portmapper) RPC scanning, fragmentation
scanning, and flexible target and port specification.