Hook does not come to the straight. It comes from the side and hit on your face. When you are in fighting competition, you wear gloves, head guard and different protection. In a street fight, you will not have all those to give some sort of protection.
So how can you defend yourself against hook punch?
First of all, protect your head. Keep your hands up and cover your head. If you can cover your head properly, hook punch will not hit on your face. If the attacker wants to hurt you pretty bad, he/she is not going to stop there. As soon as you cover your head and defend the hook, attack the person.
Since there are no rules in a street fight and anything could happen. So be prepared and observe the surroundings. It can give you a signal and you can be in a position to stop it before happening.
