how do you stop rodents chewing cables?

i thought my rats were not chewers and neglected to watch them that closely when they had their run. they were housetrained and there was nowhere they could get trapped in. however i have now discovered that, while they don't chew anything else except food, they appear to love cable plastic and have made a right mess. since i do not want them to cut off my internet access, phone line or worse electrocute themselves i need to stop this. if you have hamsters, rabbits, rats or any other beasties prone to knawing what do you do to stop them munching through cables? i'm going to ask at the pet shop but any tips would be appreciated. i think you can get a spray - does this work?