thats its tough. but a good idea too.

AI is a very large subject. For that purpose you can use Neural networks (NN). Its NOT A easy think to do, so if you want do follow AI path, you will need a lot of research and patience.

You can achieve some 'inteligence" on your IDS creating a NN that has the ability of "learning".

then you will train your NN, presenting to it patterns representing "intrusion" and "normal behavior". After some time, NN will start to recognise pattern.

But is too large to explain here. you will need to read the basics of NN and try by yourself.

Other "fields" of AI are: Genetic Algorithms (GA) and Fuzzy logic. Ga is pretty easy (the concept, not the implementation) but Fuzzy logic is kinda weird.

good luck!