When you do something wrong or bad, that's misbehavior. If your little brother hides your homework, intentionally dumps his cereal on the floor, and draws on the walls with permanent marker, you might say he's an expert in misbehavior.
Whether an activity is mere naughtiness or more significant misconduct, it all falls under the category of misbehavior. When a politician pays someone to stay quiet about his misbehavior, he's added additional misbehavior to the record. If you know that behavior means the way you act, it's easy to see what happens when you add the prefix mis-, meaning "bad".