Over the course of 6 months, 409 people clicked on an ad that offered infection for those with virus-free PCs. Didier Stevens, who ran the ad via Google Adwords, works for Contraste Europe, a branch of the IT consultancy The Contraste Group. Stevens says that he got the idea after picking up a small book on Google Adwords at the library and finding out how easy and cheap it is to set up an ad. "You can start with a couple of euros per month. And that gave me an idea: this can be used with malicious [intent]. It"s a way to get a drive-by download site on the first page of a search."
Stevens bought the drive-by-download.info domain, set up a server to display a "Thank you for your visit" message and to log the requests. No PCs were harmed in this experiment, he emphasizes. Then he started the Google Adwords campaign, using combinations of the words "drive-by download" along with the ad. His ad was viewed 259,723 times and clicked on 409 times, for a click-through rate of about 0.16%. The experiment cost him $23, or 6 cents per click/potentially infected machine.
Of the 409 people who clicked, 98% were running Windows machines, according to the user agent string, which is a text string that identifies a Web site visitor to a server. Users using different versions of IE, Safari, Opera, Firefox and SeaMonkey all clicked the ad. Stevens says that he designed his ad to make it look fishy, but he had no problem getting Google to accept it and has had no complaints to date. And, although a healthy amount of people clicked on it, he said there"s "no way to know what motivated them to click on my ad. I did not submit them to an IQ-test." Stevens said he"s sure he could get much more traffic if he invested more in his Google Adwords budget and came up with a better designed ad.