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The U.S. Justice Department and the FBI were granted unprecedented authority this week to seize control over a criminal botnet that enslaved millions of computers and to use that power to disable the malicious software on infected PCs.
Sample network diagram of Coreflood, Source:FBI
The target of the takedown was “Coreflood,” an infamous botnet that emerged almost a decade ago as a high-powered virtual weapon designed to knock targeted Web sites offline. Over the years, the crooks running the botnet began to use it to defraud owners of the victim PCs by stealing bank account information and draining balances.
Coreflood has morphed into a menacing crime machine since its emergence in 2002. As I noted in a 2008 story for The Washington Post, this is the same botnet that was used to steal more than $90,000 from Joe Lopez in 2005, kicking off the first of many high profile lawsuits that would be brought against banks by victims of commercial account takeovers. According to the Justice Department, Coreflood also was implicated in the theft of $241,866 from a defense contractor in Tennessee; $115,771 from a real estate company in Michigan; and $151,201 from an investment firm in North Carolina.
By 2008, Coreflood had infected some 378,000 PCs, including computers at hospitals and government agencies. According to research done by Joe Stewart, senior malware researcher for Dell SecureWorks, the thieves in charge of Coreflood had stolen more than 500 gigabytes of banking credentials and other sensitive data, enough data to fill 500 pickup trucks if printed on paper.
On April 11, 2011, the U.S. Attorney’s Office for the District of Connecticut filed a civil complaint against 13 unknown (“John Doe”) defendants responsible for running Coreflood, and was granted authority to seize 29 domain names used to control the daily operations of the botnet. The government also was awarded a temporary restraining order (TRO) allowing it to send individual PCs infected with Coreflood a command telling the machines to stop the bot software from running.
The government was able to do this because it also won the right to have the Coreflood control servers redirected to networks run by the nonprofit Internet Systems Consortium (ISC). When bots reported to the control servers – as they were programmed to do periodically – the ISC servers would reply with commands telling the bot program to quit.
ISC President Barry Greene said the government was wary of removing the bot software from infected machines.
“They didn’t want to do the uninstall, just exit,” Greene said. “Baby steps. But this was significant for the DOJ to be able to do this. People have been saying we should be able to do this for a long time, and nobody has done what we’re doing until now.”
No U.S. law enforcement authority has ever sought to commandeer a botnet using such an approach. Last year, Dutch authorities took down the Bredolab botnet using a similar method that directed affected users to a Web page warning of the infection. Last month, Microsoft took down the Rustock spam botnet by convincing a court to grant it control over both the botnet’s control domains and the hard drives used by those control servers.
