internet AI

how do I create an AI that will take control of the internet and how do we combat such an AI?

You just watched Terminator, didn't you?
Take a look into neural networks, genetic algorithms and cellular automata and try to combine ideas from all of those. Try to find a system that has a strong attractor and then modify the system so that it is attracted to intelligence.
I wish you good luck. Personally I have given up. Even if you find a "God algorithm" that evolves intelligence insanely fast, you still need to create a good fitness function (even if P=NP, the computer can't read your mind). Maybe use other fitness functions to evolve the fitness functions themselves, or even more abstract fitness functions to evolve those "hyper-fitness-functions". Again, I honestly wish you good luck. Don't let anything or anyone bring you down. Report back if you accomplish anything (or don't, I will see it anyway).

how do we combat such an AI?
One idea is to make another AI like the first one, and watch those two fight. Isn't this going to be fun?