Someone else is using your Google Adsense code on their website without permission?

Have you found out that someone else is using your Google Adsense code on their website without permission? You are not alone. A simple Google search indicate that several others are facing similar issues. Is there something to worry about? Yes. At first it sounds okay that someone else chose to use your Google Adsense code and that the revenue from that website (if the site has some traffic) will be yours, but on the other hand it is risky for your Google Adsense account as it might have been done with bad intentions to spoil your Google Adsense status. Such malicious usage may lead to Google Account being banned. So what can be done?