The bad behavior was taught to the kitty by his owner. They probably smacked the cat around to play with him when he was a kitten. Now that the cat is 6-8 months old it thinks it is playing. The bad behavior can be unlearned by telling him no in a loud tone and putting the kitty in a cat carrier for 20 minutes time out when he bites, playing with him with a cat toy like a string on a stick. Kitty treats and praise when he does not bite. The treats stop if he bites or scratches.