When you visit a webiste all these information are sent to that website and will be recorded by default. They are a.Your PC’s IP address b.Operating system c.MAC Address d.Screen resolution e.Browser information( IE/Firefox ). Google will compare 1. Above information collected from your adsense login and 2. Above information collected from PC from which the ads were clicked
If both 1 and 2 match then your adsense account might be suspended anytime.