Security researchers have discovered a way to shut down or seriously impair a Google Adwords advertising campaign by artificially inflating the number of times an ad is displayed. By running searches against particular keywords from compromised hosts, attackers can cause click-through percentage rates to fall through the floor.
This, in turn, causes Google Adwords to automatically disable the affected campaign keywords and prevent ads from being displayed. By disabling campaign keywords using the technique, cybercrimals could give their preferred parties higher ad positions at reduced costs, according to click fraud prevention specialists Clickrisk.
"By disabling targeted keywords across many advertisers' campaigns simultaneously by artificially inflating the number of times an ad is displayed an attacker can secure a higher ad position," explains Clickrisk.com chief exec Adam Sculthorpe. The attack - dubbed keyword hijacking - is difficult to prevent because it takes advantage of a design feature of Google Adwords rather than a flaw, he added. Clickrisk came across the attack in investigating why the click through rates of one of its clients - which had been running at a steady rate - dropped to zero for no apparent reason. Subsequent monitoring and forensic testing revealed that a botnet made up of open proxies in China was responsible for the attack.
High—cost-per-click (CPC) advertisers in niche markets are particular vulnerable to the keyword hijacking attack. "Once keywords are disabled they can't be re-enabled and attacks can go undetected for some time," Sculthorpe told El Reg. When keywords are disabled an advertiser must erase all campaigns featuring the affected keywords and create a new campaign as a workaround.
Although the true scope of the problem remains unclear, Clickrisk security analysts believe the keyword hijacking attack may be widely exploited. Clickrisk advises users to monitor click-through rates and traffic levels, log into Google Adwords campaign frequently and check that keywords are not disabled.
The incidence of click fraud risk exposure in general is on the rise. According to Clickrisk’s chief risk officer, Jack Bensimon, "our clients have experienced substantial losses ranging from 20 – 65 per cent of their total click costs." Bensimon believes that "managing business risk is a critical component of online advertising" and further recommends that "online marketers should be vigilant and regularly monitor keywords". ®