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1 edit | Mystery web infection grows - can you help? From The Register
16 Jan 2008 - said by The Register :
Mystery web infection grows, but cause remains elusive
Five days ago, we wrote about the infection of several hundred websites that was unlike anything seasoned researchers had seen before. Mary Landesman, a cyber gumshoe who first brought it to public attention, asked for help from other security pros in figuring out how the unusual new technique worked. And help is what many of her peers have provided.
The sites host malicious javascript that is spontaneously created and randomly named only after a visitor hits the home page. That's unlike any other mass infection most researchers have seen before. Usually, infected sites merely host pointers to attacker-controlled servers, which in turn are used to host malware with static file names.
The innovative technique is much more than an academic curiosity. Because the rogue code does not exist on any server until an end user visits it, the javascript remains invisible to site administrators. The randomness also prevents most antivirus programs from detecting the javascript. Equally frustrating, it prevents researchers from running a simple web search that ferrets out every web address where the attack code is hosted.
From her perch at ScanSafe, a company that provides real-time intelligence to large businesses about malware-spreading sites, Landesman could see several hundred websites exhibiting the odd behavior. Based on intelligence from firms with sensors elsewhere on the net, it turns out that the number of infected sites is much bigger.
According to independent reports released earlier this week by SecureWorks and Finjan, 10,000 or more websites are similarly infected. As of Tuesday, almost all of these were still infected. They are churning out malware, which preys on at least nine different vulnerabilities in programs such as the QuickTime media player, Yahoo! Messenger and Windows operating systems to install a backdoor on end users' computers.
Once the malware successfully finds an unpatched vulnerability, it installs the Rbot Trojan, or one of its variants. Many antivirus programs still fail to detect the exploit.
The infection dates back at least to late November, according to this thread, which was dredged up by a Reg reader in response to our earlier story. The online discussion shows web administrators from many companies reporting infections that were using multiple exploits to attack end users, and documents their difficulty in disinfecting the systems.
Landesman also reports how hard it is to remove the attack code from tainted web systems. Over the weekend, she noticed two modules - one called mod_bwlimited and the other enable_dl - in the Apache webserver that were responsible for transmitting the randomized malware onto end users' machines. But when she disabled them, she was dismayed to find the changes reversed and that the machines had soon resumed their attacks.
According to ScanSafe and SecureWorks, the attacks are the result of a web-side rootkit that actually creates and transmits the randomized files after a victim visits the site.
But so far no-one - not ScanSafe nor SecureWorks, Finjan or any other researcher we've contacted - has any idea how these mostly mom-and-pop ecommerce sites are getting infected in the first place. The vulnerability is unlikely to reside in Apache, given the sheer number of variants that different infected machines are running.
Infected sites also use a wide number of different web hosts, making that an unlikely entry way for attackers. While Cpanel, a tool for remotely administering the site, appears to be modified by the infection, Landesman says her research suggests that is also not the way attackers gain access.
This is a problem, because if you don't know how thousands of of machines are being commandeered, you can't prevent tens of thousands more from suffering the same fate.
"Every time I think I have some common thread, I find some exception to the rule," says Don Jackson of SecureWorks. "How do we stop websites from experiencing this again? We really don't know what controls we need to put in place."
What's really needed now is for operators of websites that are infected to step forward and allow a trusted researcher to inspect the machine. (One webmaster from a site mentioned in Friday's article volunteered to help Landesman, but by then he had already wiped his system clean, removing crucial evidence in the process.)
If you've seen the behavior described above lurking on your site, please leave a comment below, or contact your reporter using this link. Similarly, if you're a researcher with insight into this program please do the same.
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