Blacksn0w

Geohot's runtime unlock for baseband 05.11.07 (used by the iPhone 3G & 3GS). blacksn0w exploits the AT+XEMN Heap Overflow, and can be installed via blackra1n or its Cydia repo (http://blackra1n.com/).

Installing
blacksn0w can be installed by adding http://blackra1n.com/ as a Cydia repository.

If the iPhone was jailbroken with blackra1n, the blackra1n app can install blacksn0w. Run the blackra1n app on the SpringBoard, and tap ra1n to update the app. Load blackra1n.app again and choose the 'sn0w' option to install. Commcenter will restart and you will have an unlocked iPhone 3G(S).

Links

 * Source code - msftguy (Reversed blacksn0w dylib, refactored to support safe mode and work on multiple OS versions.)