Seth Rosenblatt/CNET

Hackers who spent their teen years phone-phreaking -- breaking into telephone networks and making free calls -- have created their own GSM network at Defcon and are using creative and silly apps on highly customized Android phones.

The Ninja hacker group is giving the phones away to people who have contributed to the community, and to their lucky friends. The phones and accompanying lanyards serve as "badges" that provide entrance to the annual Ninja party tonight. (Defcon attendees can also get in by donating blood or signing up to donate bone marrow, or donating money to the Electronic Frontier Foundation.)

The phones are HTC One V phones running Android 4.0.3. Calls can be routed over the private GSM network or over Defcon's Wi-Fi network. The network is not encrypted and there is no emergency call phone number.

The "Ninja Tel" network is "the biggest OpenBTS (base transceiver station) network ever," said Ninja Michael J.J. Tiffany. OpenBTS networks are designed to allow for software-based switching technology that can be housed in small spaces, such as a van.

The Ninja Tel van, complete with official looking logo and hard-hat wearing workers, has a GSM base station; a 12-foot antenna; networking and Web app servers; and other equipment and is parked in a large room at Defcon. The project took about 10 months to complete, Tiffany said.

There are 650 phones on the private network, with people making phone calls, texting, chatting, holding conference calls, and playing a sword-fighting game. There are additional apps being created by people who are using the phone through Android's IDE (Integrated Development Environment).

People choose their own phone number and username and can have their photos taken so that their face shows up in everyone's contact list. Once the customized Ninja SIM card is inserted, a special terms of service written by a Ninja who is a lawyer is displayed and the phone receives a call with a fun welcome message recorded by Pat Fleet, who is the voice of AT&T.

The interface has a retro look and feel with screens reminiscent of the yellow pages and other classic elements, created by Pinguino, a designer at Universal. Ninja attention to detail is seen in every interaction, such as the sword sound that's made by the phone when the screen is unlocked.

A popular app is BoozeFone, a play on MovieFone, which gives options such as press 1 for Vodka, 2 for Jack Daniels, and 3 for PBR and has a humorous recorded audio message for each. People can notify the system that they have booze and what type, and when someone calls in and requests that item the two will be connected.

There is a vending machine app that interacts with customized Coke machines to dispense swag, but Tiffany declined to say exactly what, not wanting to spoil the surprise for people using the machines at the party.

Ninjas declined to say how much the operation cost for the phones and all the equipment, paid for and otherwise supported by Facebook, Zynga, AllJoyn, and Lookout, whose workers worked on the Android development.

"The goal was to create a network that could be explored to give people an experience they haven't had since we were kids," Tiffany said. "It's not just a phone network. It's a phone network that has a lot of goodies.... We laid down the infrastructure and people are bringing the party to this network. It's an interactive experience."

Given that it is a hacker conference it's no surprise that people are trying to hack the network and take it down, but so far there has been only one known attempt to jam the network, and it failed, Tiffany said.

Creating a phone network purely for play is classic hacker MO and, in particular, typical of this group.

"We are a constructive group," Tiffany said. "We have a name and we did it not by being bad. Not breaking anything or taking anything down. We're creating our own network. That's Ninja style."