The operation, which marks Microsoft's seventh botnet takedown to date, began in early 2012, when researchers turned their attention to the infamous Citadel malware. Citadel first appeared in 2011 and is based off of the source code for the even more notorious Zeus malware that was leaked publicly that year.
According to Microsoft, Citadel has affected upward of 5 million people, with the largest numbers of infected machines residing in the U.S., Europe, Hong Kong, Singapore, India, and Australia. Once on a machine, the malware monitors and records the victim's keystrokes in order to steal his identity and bank login information in order to loot his accounts.
"The harm done by Citadel shows the threat that botnets, malicious software, and piracy pose to individuals and businesses around the world," said Brad Smith, Microsoft general counsel and executive vice president of Legal and Corporate Affairs, in a statement. "Today's coordinated action between the private sector and law enforcement demonstrates the power of combined legal and technical expertise and we're going to continue to work together to help put these cybercriminals out of business."
Last week, Microsoft filed a suit in a federal district court in North Carolina to get authorization to cut off communication between 1,462 Citadel botnets and the millions of computers in their grasp. On June 5, U.S. Marshals accompanied Microsoft to two data hosting facilities in New Jersey and Pennsylvania to seize computer servers and other evidence. Microsoft also provided information about the botnets' operations to Computer Emergency Response Teams (CERTs) around the world so they could take action as well.
"Citadel is aimed at a more 'exclusive' attacker market than its more widespread predecessor, Zeus," blogs Piotr Krysiuk, a researcher with Symantec's Security Response Team. "The Citadel kit is sold through underground Russian forums and typically costs around $3,000, compared to $100 for the SpyEye and leaked Zeus kits. Citadel users will also have to fork out a further $30 to 100 to purchase Web inject code for the banks that they wish to target. Additionally, even if attackers have that money to spend, there is a strict vetting process with referrals required for new purchasers."
According to FBI executive assistant director Richard McFeely, the operation represents the future of addressing malware threats.
"Creating successful public-private relationships -- in which tools, knowledge, and intelligence are shared -- is the ultimate key to success in addressing cyberthreats and is among the highest priorities of the FBI," he said in a statement. "We must ensure that, as cyberpolicy is developed, the ability of the private sector to coordinate in real time with the FBI is encouraged so that a multiprong attack on our cyberadversaries can be as effective as possible."
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