Criminals who operate large groupings of hacked PCs tend to be a secretive lot, and jealously guard their assets against hijacking by other crooks. But one of the world’s largest and most sophisticated botnets is openly renting its infected PCs to any and all comers, and has even created a Firefox add-on to assist customers.
The TDSS botnet is the most sophisticated threat today, according to experts at Russian security firm Kaspersky Lab. First launched in 2008, TDSS is now in its fourth major version (also known as TDL-4). The malware uses a “rootkit” to install itself deep within infected PCs, ensuring that it loads before the Microsoft Windows operating system starts. TDSS also removes approximately 20 malicious programs from host PCs, preventing systems from communicating with other bot families.
In an exhaustive analysis of TDSS published in June, Kaspersky researchers Sergey Golovanov and Igor Soumenkov wrote that among the many components installed by TDSS is a file called “socks.dll,” which allows infected PCs to be used by others to surf the Web anonymously.
“Having control over such a large number of computers with this function, the cybercriminals have started offering anonymous Internet access as a service, at a cost of roughly $100 per month,” the researchers wrote. “For the sake of convenience, the cybercriminals have also developed a Firefox add-on that makes it easy to toggle between proxy servers within the browser.”
The storefront for this massive botnet is awmproxy.net, which advertises “the fastest anonymous proxies.” According to Golovanov, when socks.dll is installed on a TDSS-infected computer, it notifies awmproxy.net that a new proxy is available for rent. Soon after that notification is completed, the infected PC starts to accept approximately 10 proxy requests each minute, he said.
“For us it was enough to see that this additional proxy module for tdl4 was installed directly on encrypted partition and runs thru rootkit functionality,” Golovanov told KrebsOnSecurity. “So we believe that awmproxy has direct connection to tdl4 developer but how they are working together we don’t know.” The curators of AWMproxy did not respond to requests for comment.
The service’s proxies are priced according to exclusivity and length of use. Regular browser proxies range from $3 per day to $25 monthly. Proxies that can be used to anonymize all of the Internet traffic on a customer’s PC cost between $65 and $500 a month. For $160 a week, customers can rent exclusive access to 100 TDSS-infected systems at once. Interestingly, AWMproxy says it accepts payment via PayPal, MasterCard, and Visa.