We are not culturally inclined to suicide attacks, so there is only one weapon that can be remotely deployed and that destroys most evidence of its origins. A Nuke. Analysis can determine the origins of the fission products of a detonated bomb, but since we are loaded with old Soviet enriched Uranium to burn in our reactors it will be impossible to prove the weapon's origins.
As we slip into that night that is a modern Security State we have only the memory of the time when we were a truly free people and we could speak our minds and elect our government. It was fun while it lasted.