Doomsday machines

Dr Strangelove and the real Doomsday machine - Times Online

Here's an interesting review of a book about nuclear doomsday machines. One was imagined and not built (it's a little hard to see the political/military tactical value of ending all life on earth,) but the other was built in Russia and is, presumably, still in action. This later one is an automated "return fire" computer, and does indeed sound a bit of a worry.