Yeah, it's called clickbombing: http://empireflippers.com/clickbombing-and-click-fraud/ (NB, Have no idea whether that's a reputable site, but the analysis in that blogpost is reasonably in depth).

If you're lucky, you catch it, report it to Google & they just take the income away (as it should be). If you're unlucky, Google decides that you're trying to defraud them & their ad clients and kills your entire AdSense account for all the sites you have registered with them. A scorched earth policy being the best possible policy apparently.