Abstract: This invention is a real-time system that detects click fraud and blocks those click fraud. This system will be used as an arbitration system to evaluate the quality of every click referred from PPC publishers, thus helping advertiser saving money. The invention uses innovative matching between two logs, client side log and server side log, to find out software click and detect abnormal activities, such as no mouse movement, no mouse clicks, repeat clicks etc. The system includes three parts working cooperatively: a database for logging user click parameter and reporting click fraud, web servers with filter program such as ISAPI filter, CGI or other server side script program, and tracking code inserted to a web page, executed on client computer. The system can also block any fraudulent traffic in real time.