If my ads receive robotised clicks in an unlimited amount, it's quite clear that my AdSense account will be banned. Are there such scripts or services? How can I protect my website against this kind of scripts?
See from what country comes those maybe isn't a robot but a malicious mind a hateful person can do it. If its a robot you can remove those via .htaccess also you can block the IP if is a hateful person.
If you use wordpress there is click-fraud plugin to use with. You have to place your ads in a special format to have them protected against multiply clicks: Requirements: Use the following div container around your ads: <div class='cfmonitor'>ADSENSE CODE HERE</div> Your adsense account will be safe!