It can be like a scene from Jaws. You can imagine the music playing in the background as you walk down the dark hallway, or near furniture where it could be lurking underneath. Just as you think you've made it safely passed, it springs from its hiding place and latches onto your legs. This isn't done with playful kitten joy, but with seemingly vicious intent to draw blood.
 
If you know this scene all too well, then you live with a cat that attacks without provocation. Some cats may turn on you when you are petting them. They may seem relaxed and happy one moment and then angry and fierce the next, leaving you with a bloody hand.
 
There are several reasons why a cat acts out with unprovoked aggression. Understanding the cause can help you decide how to work on solving this feline behavior problem.
 
Health issues
A cat that is sick for any reason may have a sudden personality change. A once sweet and affectionate cat may now be aloof and aggressive. A cat with an injury may attack when you touch a spot that hurts. Take your cat to the veterinarian to find out if there is a medical reason for your cat's behavior.  
 
Lack of socialization
Kittens that are not handled regularly by people at a young age grow up to be cats that don't know how to properly socialize with people. This can turn into aggression because they may fear people or just don't know how to properly interact with people. Territorial behavior
The cat may be protecting its territory from intrusion. In such cases, the cat has not accepted humans as friends. They see people as enemies who are encroaching on their territory.
 
Hyperesthesia
Hyperesthesia is a recognized anxiety disorder in cats. Cats with hyperesthesia are overly sensitive to any touch along the spine and tail. When pet down the back, they may have muscle spasms, become aggressive, or even appear to hallucinate. Experts do not completely understand this condition, but two theories are that it is a type of seizure disorder or a form of obsessive compulsive disorder.
 
How to stop a cat that attacks
If your cat's aggression is not caused by a medical condition, then you can take steps at home to help your cat feel more comfortable around people. Make sure your cat has a retreat area where it can hide, feel safe, and take a break from people. A covered cat bed or tall cat tree works well as a kitty retreat. When your cat is in this space, leave it alone. Spend time with your cat feeding it favored cat treats. Feed the treats while petting to help your cat associate petting with good things. Don't ever hit or yell at your cat, as this will only reinforce their fear and aggressive behaviors.
 
If you have tried all these things at home and your cat is still aggressive, then ask your veterinarian for help. Your vet can prescribe medications to help with cat behavior problems. A veterinarian can also recommend a cat behaviorist who can come to your home and give you more advice that is specific to your individual cat's personality and behavior.