Stuxnet, is a recently discovered, military grade, precision crafted piece of weaponized malware created by unknown parties to attack, control and presumably destroy a complex industrial target somewhere in the world.

But only one specific target. The software 'fingerprints' every system it infects, looking for some so far unknown marker. If it doesn't find what it is looking for, it does nothing. However, experts have found that it then waits, checking every 5 seconds, looking for something very specific. We do know that the last bit of code, which is the key order to destruct, is called DEADF007.

Who did it is unknown, what it's target is is unknown, but it's sophistication and complexity required a lot of money and expertise to create, and thus it was probably sponsored by a nation state.

Possible target - Iran's Bushehr nuclear power plant?