Wardialing (or war dialing) is a technique to automatically scan a list of telephone numbers, usually dialing every number in a local area code to search for modems, computers, bulletin board systems (computer servers) and fax machines.
The repeated incoming calls are especially annoying to businesses that have many consecutively numbered lines in the exchange, such as used with a Centrex telephone system.
Eventually, the etymology of the name fell behind as "war dialing" gained its own currency within computing culture.
[2] The popularity of wardialing in 1980s and 1990s prompted some states to enact legislation prohibiting the use of a device to dial telephone numbers without the intent of communicating with a person.
Related to wardriving is warchalking, the practice of drawing chalk symbols in public places to advertise the availability of wireless networks.
The term is also used today by analogy for various sorts of exhaustive brute force attack against an authentication mechanism, such as a password.