In July, a British man was cleared of charges that he had downloaded child pornography. How? He claimed that a trojan-horse program had been the culprit; the program had downloaded the porn without his knowledge or consent. Now, a teenager in the U.K. has successfully used this defense for a hacking crime — he claimed a trojan horse had infected his computer and used it to break into a remote corporate server. As CNN.com reports:

Caffrey had been charged with breaking into the system and crippling the server that provides scheduling information for all ships entering the world’s sixth-largest port.

Although authorities traced the hack back to Caffrey’s computer, he said that someone must have remotely planted a program, called a “trojan,” onto his computer that did the hacking and that could have been programmed to self-destruct.

It’s a fascinating defense — because while it might at first blush seem scoffworthy, the fact is that computers these days are crammed full of more spyware than ever before. There are probably a half-dozen bots on your computer as we speak. They’re communicating with the outside world, sending out requests, transmitting data, doing stuff of which you have no clue.

This is yet another aspect today’s Turing world. We spend our days trying to screen out spam, or to pass spambot-screens so that we can use services like Yahoo mail or Ebay. In effect, we’re constantly attempting to verify who’s actually human, while also trying to prove our own humanness. The flip-side is also true: In a trojan-horse defense, you have to prove that the bot did it — that when your computer sent out that HTTP request to load a page from a sketchy child-porn site, that it wasn’t really you. There were no human hands on the keyboard.

I predict this area is going to become indescribably weirder in the years to come.