Federal marshals and representatives of Microsoft and Symantec raided two data centers Feb. 6, shutting down a botnet that the companies estimated attacked at least 8 million computers in the last two years, rerouting search queries and robbing search engine firms of potential revenue.
Known as the Bamital botnet, the network of compromised computers hijacked search queries to servers controlled by the bot operators, returning custom—and ofttimes, malicious—search results to earn the controllers affiliate fees. The takedown, dubbed Operation b58, is the sixth for Microsoft, which has targeted bot operators using legal tactics and technical research to disrupt their operations through an initiative known as the Microsoft Active Response for Security (MARS) program.
"While the Bamital botnet defrauded the entire online advertising platform, which is what allows the Internet and many online services to be free, what's most concerning is that these cyber-criminals made people go to sites that they never intended to go and took control of the computer away from its owner," Richard D. Boscovich, assistant general counsel for Microsoft's Digital Crimes Unit (DCU), said in a blog post.
Users of computers infected with Bamital would be redirected to Websites that paid an affiliate fee to the bot operators. In addition, the eventual destination would sometimes attempt to install malicious software on the victim's computer. Searching for the site of Symantec's Norton Internet Security product, for example, led to a rogue antivirus site that would install malware.
The takedown is the latest in a string of private actions taken by security companies against bot operators. In the last three years, Microsoft and a number of other security companies have taken the fight to criminals by using technical and legal means, as well as cooperating with law enforcement, to attempt to shut down the bad guys' botnets. The networks of compromised computers give cyber-criminals control of their own "cloud" of computers, from which they can mine valuable data, conduct account fraud, send out spam or attack other networks.
In the Bamital takedown, Microsoft and Symantec have co-opted the cyber-criminals' ability to redirect search queries and will instead display a page that directs infected users to resources to help them clean their systems.
"Getting this process started should take less than 10 minutes and the scan can be completed in generally less than an hour, but may vary depending on your system and software used," Tim Rains, director of product management in Microsoft's Trustworthy Computing group, said in a statement. "You do not need to do anything during the scan."
The DCU is a small group of cyber-crime experts at Microsoft that uses legal and technical means to investigate and take down botnet infrastructure. On Jan. 31, Microsoft filed a civil lawsuit against the operators of Bamital seeking a court order to sever all communications between the botnet and victims' compromised computers. Six days later, the U.S. Marshals Service helped Microsoft technicians seize data and servers at data centers in New Jersey and Virginia.