Sudden change in behavior can mean illness or pain so take him to a veterinarian for a check up. Changes in the environment (moving/new pet) can also be the cause.
These are both warning behaviors that tell you the cat is uncomfortable. The cat may be scared, or he may be in pain. If a cat's hissing and growling are ignored, it may escalate to biting.
He could be under stress or in pain.Your vet can rule out any health problems that could be causing him pain. If he is healthy, try contacting a local behaviorist.
Cats hissing just means it's 1. In pain. 2. Feel threatened. 3. Bothered 4. Other cats on their turf. Hissing is a defense if anything not bad behavior.
