cat that likes to ambush

I have a orange male tabby cat who is 1 years old. Lately, he likes to ambush(jump) on my families back,with his claws out,purring all the way. Is this normal? and how can i stop this behavior because i need to keep my skin intact?

No it is not normal. Does he have a cat condo? A lot of toys, do you do interactive playtime with him every day? This cat is bored with a high energy output and no way to release it. You can get an empty cardboard box (large) big enough that he can get into it and run around, and drop some pingpong balls in the box. Cut some holes in the box (cut the flaps off the sides too, and make sure the holes are big enough that the cat can easily jump through them to get inside, and keep them off the ground level, so the balls stay inside the box.