Scareware Using Bing Results To Expand Attack

A new scareware attack serving rogue antivirus advertisements has been targeting Swiss and Dutch websites. Interestingly, the attack uses a novel technique to lure search engine users: it relies on Bing search results to stay relevant.

On Friday, Dancho Danchev, an independent security consultant based in the Netherlands, blogged that he'd been tracking "a blackhat SEO campaign that's persistently compromising legitimate sites within small ISPs in the Netherlands and Switzerland, for scareware-serving purposes."

He said, "Although this beneath-the-radar-targeting approach is nothing new, it once again emphasizes a well-proven mentality within the cybercrime ecosystem." Namely, target "hundreds of thousands of low-profile sites," using them to poison search engine results with fake links, and attackers can generate more traffic to those links than if they'd targeted more high-profile and better-secured websites.

Typically, these rogue antivirus -- or as Google calls it, fake AV -- campaigns infect numerous websites as fast possible, before the search engine operators catch on, and this attack was no exception. "In many cases we were looking at mass compromises where a server hosting hundreds of websites was compromised," blogged Bojan Zdrnja, at the SANS Internet Storm Center, on Tuesday.

He said the new attack resembles rogue AV campaigns seen this past June and July, in which attackers infected all PHP files on a targeted website. This attack, however, only places a single, master PHP script -- often dubbed "page.php" or "wp-page.php" -- which then "phones home" for further instructions and downloads additional PHP scripts as required.

Whenever a search engine crawler indexes an infected website, the master script takes the keyword sought by the crawler and requests the top 50 results for that keyword from Bing. The master script massages the Bing results, strips out any JavaScript, again phones home -- receiving 100 links to other compromised websites -- and uses the Bing results and links to create an index.html page, which it returns to the web crawler.

Interestingly, the master script also hides itself, refusing to display if accessed directly. Instead, it only responds to web crawler requests, or to referrers, meaning someone clicked on a rogue AV link in search engine results. At that point, "the browser is redirected to a third site -- and possibly fourth -- that displays the infamous RogueAV warnings," said Zdrnja.

He said this attack is an obvious improvement on prior versions. "Yesterday I checked Google and I was able to find thousands of poisoned results pointing to such compromised websites," he wrote on Tuesday. "While the search engine operators do a lot of work to prevent poisoning like this, it is clear that the bad guys are not resting either and that they are developing new poisoning techniques constantly."