Well-known iOS jailbreak developer and hacker Majd Alfhaily was intrigued when read about MDSec's black box hardware brute force for iOS devices. The tool, which runs over a USB connection, tries every possible passcode combination in an attempt to unlock an iPhone secured with a simple passcode.
The downside of such a tool, is that each PIN entry takes approximately 40 seconds, so it could take more than 110 hours to brute force an iPhone. Majd, being the curious person that he is, devised a way to do it in a fraction of the time using only software. The only caveat, if you even want to call it that given what it does, is that the device must be able to run unsigned code, i.e., the device must be jailbroken.