War dialing is the term given to accessing a network illegally over a compromised phone line. Popular tools include THC war dialer and phone sweep.
Scanning is a method adopted by administrators and crackers alike to discover more about a network
There are various scan types - SYN, FIN, Connect, ACK, RPC, Inverse Mapping, FTP Bounce, Idle Host etc. The use of a particular scan type depends on the objective at hand.
Popular scanning tools include Nmap, Superscan, Cheops etc
TCP connection is established through a three-way handshake.
Ways to subvert a standard connection include HTTPort, HTTP tunneling, using proxies, SOCKS chains and anonymizers.