2600 may refer to any of the following:
1. The frequency in hertz that AT&T initially used to indicate when a line is free. In 1974, John Draper aka Captain Crunch discovered a breakfast cereal children's whistle was capable of making this tone. He and others used this technique or similar techniques in conjunction with a blue box to generate the 2600 hertz tone and make free long distance calls around the world. These individuals came to be known as phreaks.
2. 2600 is also a commonly used name for news or information containing information about hacking and phreaking.
3. The 2600 name commonly associated with the early Atari VCS (Video Computer System) gaming system.