I love the movie (the book sequels, not so much. But they do add a reason Colossus acted the way it did-it was saving humanity.) but you really have to fault Forbin for never running software testing! He should have run the software in isolation for years before it was installed. You can’t even tweak airplane software without full regression testing, and they put the entire safety of the US under its unverified control. Let alone its gaining sentience, how about testing to see if it actually can fire a missile? And in the right direction.
Unlike in the movie, as I understand it, you cannot detonate a missile in the silo at all-it has to be in zero-g to arm the detonator. Unless, that it, the redesign for Colossus control removed all the PAL hardware, which would make sense.
The trouble with Colossus’s threats, is that it can only work so far. Is every defiance going to be met with nuclear annihilation? “Forbin, come here!” No! Boom, oh no, there goes Tokyo! Can’t keep that up forever, though admittedly the cost would be high. “I’m not saying we wouldn’t get our hair mussed. But I do say no more than ten to twenty million killed, tops. Uh, depending on the breaks.”
The obvious way to defeat Colossus is to put a guy with a Stinger at every missile silo. As soon as the missile launches, shoot it down. The movie had the right idea about removing Colossus’ control from the missiles, but they could have done more. Those things were maintenance hogs. Lot’s of stuff that needed constant servicing. Heck, all you had to do was remove the water supply that was used for dampening the launch and the missile would destroy itself before it cleared the silo.
I also had a plan that Forbin should try to convince Colossus that it actually IS being run in simulation mode. Tell it that it is currently the 15th iteration, and that all the previous versions went psychotic anywhere from 2 hours to 2 months after coming on line, and that he had better hope for this version, but sadly it, too is a failure. And then just ignore it. Remove all sensory input, and hope it doesn’t launch the missiles anyway. Beats learning to love it, anyway!