ToneLoc was a popular war dialing computer program for MS-DOS written in the early to mid-1990s by two programmers known by the pseudonyms Minor Threat (Chris Lamprecht) and Mucho Maas. The name ToneLoc was short for "Tone Locator" and was a word play on the name of the rap artist known as Tone Lōc.
ToneLoc took advantage of the extended return codes available on US Robotics modems (e.g., ATX6[1]) to detect dial tones upon dialing a number and to detect when a human answered the phone in addition to scanning for other modems. Detection of voice numbers sped up the scanning process by disconnecting upon detecting a human instead of timing out waiting for a modem carrier signal. The detection of a dial tone after dialing a number allowed for users to search for poorly secured extenders which could be used to divert calls through.
On April 17, 2005, the source code for ToneLoc was released.