Yes, cats can be protective of their owners. While not all cats will show this behavior, some may become more watchful and attentive to their surroundings when they feel their owner is in danger. This protective instinct is often seen in mother cats who will fiercely defend their kittens from perceived threats. But even if your cat isn't a parent, they may still hiss or growl at someone they perceive as a threat to you. So, if you ever find yourself in a situation where your cat is acting strangely aggressive towards someone, it's likely that they're just trying to protect you.