War dialing

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War dialing or wardialing is a method of automatically scanning telephone numbers using a modem, usually dialing every telephone number in a local area to find out where computers or fax machines are available, then attempting to access them by guessing passwords.

The name for this technique refers to the 1983 film WarGames. In the film, the protagonist programs his computer to dial every telephone number in Sunnyvale, CA in order to find other computer systems. Although the technique predates the film, the name "war dialing" rapidly became popular within computing culture ^[1].

A more recent phenomenon is wardriving, the searching for Wi-Fi wireless networks by moving vehicle. Wardriving was named after wardialing, since both techniques involve brute-force searches to find computer networks.

Similar to war dialing is a port scan under TCP/IP, which "dials" every TCP port of every IP address to find out what services are available, then gaining access to them by guessing passwords or by exploiting vulnerabilities in software that runs with elevated privileges. Unlike wardialing, however, port scans will generally not disturb a human being when it tries an IP address that isn't up. Related to wardriving is warchalking, the practice of drawing chalk symbols in public places to advertise the availability of wireless networks. Despite its widespread coverage, warchalking never particularly caught on as a popular activity.

The term is also used today by analogy for various sorts of exhaustive brute force attack against an authentication mechanism, such as a password. While a dictionary attack might involve trying each word in a dictionary as the password, "wardialing the password" would involve trying every possible password.

War dialing is sometimes used as a synonym for demon dialing, a related technique which also involves automating a computer modem in order to repeatedly place telephone calls.

[edit] Trivia

Sandstorm Enterprises has a patent (US 6,490,349) on the multi-line war dialer. ("System and Method for Scan-Dialing Telephone Numbers and Classifying Equipment Connected to Telephone Lines Associated therewith.") The patent is practiced in Sandstorm's PhoneSweep war dialer.
One of the segments on the 2006 audio/visual project Greedy Baby, by Plaid and Bob Jaroc, entitled "War Dialer," is based on this concept.