In Terminator canon it is established that Skynet gains self-awareness shortly after it is brought online. Skynet then starts Judgement Day by launching a nuclear attack on either Russia or humanity in general, depending on the movie, followed by the deployment of autonomous Terminator robots.
However, Skynet lacks both the proper motive to destroy humanity and the processing power to gain sentience - in Terminator 3 Skynet's processing power is announced to be 60 TFLOPS ("per second", erroneously) while a modern gaming graphics card can dish out 5 TFLOPS.
Is it possible that the attack was actually caused by a hacker attack from a third party wanting to destroy both USA and Russia?