'Transient' Hacks Become Attackers' New Favorites

Sophisticated bad guys are increasingly sneaking in and out of legitimate Websites and search engine results, even cleaning up after themselves to erase any evidence -- a technique that some researchers are calling "transient hacking."

Roger Thompson, chief research officer for AVG Technologies, says his team has recently witnessed more and more of this stealthy behavior, where attackers jump in and out of these sites rather than set up their own more conspicuous malicious sites to infect unsuspecting users.

"If you knew a site was always bad, you could simply block it at the IP address, or the ISP could block it at its border routers," Thompson says. "But by setting it up so it’s moving all the time, [attackers force victims to] play a losing game of whack-a-mole."

Some bad guys have gone to this hide-and-seek method as a way to stay alive, rather than have their malicious sites shut down. "When I first started looking at this, they would go to a lot of trouble to hide where the exploit sites were. Now they just mass-hack everybody and realize they’re going to be shut down within a few days."

There are three main types of these transient attacks, Thompson says: attackers moving malware on and off of legitimate sites, such as the recent code injection attacks on major Websites that were reported recently; attackers swapping malware in and out of legitimate banner ads on respected sites; and attackers poisoning search engine results as a way to store their malware. "This is a sign of increased skill in hacking into Websites and tracking search engines," Thompson says.

Thompson says these transient hackers appear to be a mix -- gamers from China grabbing World of Warcraft passwords and virtual gold; identity thieves looking for bank account and credit card numbers; and a few bot herders.

iFrame hacks are insidious in that they typically can't be detected on a legitimate Webpage, he says. "iFrames are generally about one pixel wide… they’re embedded, so you can’t see them. The whole point of an iFrame is to embed some data from another site without taking you off that site. There’s nothing you can see unless you’re really alert" to it, he says.

The banner ad approach was used on the recent MLB.com and MTV.com hacks, he says. Attackers change a link in the chain of the legitimate ad (on a legit site) to a malicious one, typically swapping it in and out of the ad so it isn’t as noticeable. "These come in waves and are hard to pin down," he says.

The recent search engine transient attacks are especially clever, according to Thompson. The bad guys find a popular search term, set up a fake link on that topic, and send their bots to that link to pump up the search numbers, escalating it to the top of the search engine results. "They’re not hacking Websites, just getting the search engine to store iFrames in the searches," he says, in hopes that a user will click on the link in their search results.

Of course, savvy search engines end up detecting these malicious links and clean them out of the search caches, Thompson observes. Then the bad guys just send another 100,000 bot hits to another link, playing off another popular search term. "Search engine manipulation is the epitome of a transient hack," Thompson says.

Meanwhile, not all transient attackers bother erasing their tracks, because their time-to-live on a site or in a search engine result list is typically so short. "They know they’re going to get shut down," and that they can just do it all over again somewhere else, he says. "That makes it harder to defend."

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