Zeus botnet thriving despite arrests in the U.S., U.K.

The Zeus botnet remains a robust network that is difficult to destroy despite an international sting operation that saw dozens arrested this week for allegedly stealing money from online bank accounts.

Zeus is an advanced piece of malicious software that can intercept online banking details and initiate money transfers. It can infect computers that have software with coding flaws that have not been fixed.

Law enforcement officials arrested more than 100 people, mostly from Eastern Europe, in raids in the U.S. and U.K. this week on charges of money laundering, document fraud and conspiracy. The people were allegedly part of a large computer hacking money-laundering operation believed to have stolen more than $260 million from businesses and consumers.

While it's encouraging to see law enforcement investigate, Zeus is still a problem, said Andre' M. Di Mino, a co-founder of the Shadowserver Foundation, an organization that tracks botnets.

"It's too early to determine or enumerate any key changes to Zeus itself," Di Mino said. "It remains fully operational and the security community continues to research and track it."

Victims can become infected with Zeus by visiting Web sites that are engineered to attack visitors' computers. Once those computers are infected, the attackers can siphon data and control the PCs using command-and-control (C&C) servers. Attackers often look for vulnerable Web sites in order to install the command-and-control software, which helps hide their tracks.

The arrests appear to not have had a significant technical impact on the Zeus botnet. As of Friday, at least 170 C&Cs for Zeus are still online, according to statistics compiled by the administrator of Zeus Tracker.

The statistics are updated three times a day and come from sources such as antivirus vendors, sandbox systems and other third-party sources, said the administrator of Zeus Tracker, who did not want to be identified.

The Zeus Tracker website records some of the most important information for those who are tracking Zeus-related websites, such as which ISP is hosting an infected domain and which registrar sold the domain name.

For a C&C server to be removed from the Internet, either one of three things must happen: the Zeus bot can be scrubbed from the computer by security software; the registrar can revoke the malicious domain name; or an ISP can take the offending server that is infected offline.

But security researchers have had problems with getting action taken by some registrars or ISPs, which sometimes ignore abuse requests.

On Friday, the Zeus tracker shows that the Russian registrar Reg.ru sold 10 domain names that are now being used for Zeus-related activity. Seven of those domain names are redirecting to one domain that recently hosted Zeus files, the tracker shows. At least two of those redirect domains have been active since Sept. 7, with four more active since Sept. 12.

The most recent domain name sold through Reg.ru was added to Zeus Tracker on Wednesday. That server temporarily hosted two kinds of Zeus files that have since been removed. It is possible that the owner of that domain discovered the infection and then removed the offending files.

A Reg.ru spokeswoman said that the company would look into those domains. Reg.ru, which is run out of Russia, "always promptly reacts" to inquiries or complaints from third-parties or law enforcement agencies, she said.

The issue highlight the difficulties security researchers and law enforcement have in trying to tackle botnets, which have been purposely built to be robust and redundant, much like how corporations structure their own IT systems.

But the security community has had some success in weakening and nearly wiping out botnets, but it has taken highly coordinated efforts.

Earlier this year, Microsoft petitioned a court to compel VeriSign, the .com registry, to remove 277 ".com" names from its rolls. That action cut off communication between the Waledac botnet's C&Cs and its infected troupe of computers.

Simultaneously, Microsoft recruited a team of crack computer security researchers who were able to infiltrate Waledac's peer-to-peer control system and command those infected machines to report to their own servers, cutting the cybercriminals off from their own botnet.

It doesn't appear that there are similar efforts under way to do a technical take down of Zeus to coincide the arrests. And to mount one would be difficult, said Thorsten Holz, an assistant professor of computer science at Ruhr-University in Bochum, Germany, who participated in the Waledac action.

Since criminal groups can license the Zeus software from its development group, they can set up their own C&Cs, Holz said.

"This leads to the huge number of C&Cs, which in turn render Zeus take downs in a coordinated fashion pretty hard," Holz said. "And even if many of the current C&Cs are taken down, new groups will likely emerge that run new C&Cs.

"Nevertheless the arrests are a good signal in my humble opinion since they show that there are investigations in this area which are successful," he said.

Send news tips and comments to jeremy_kirk@idg.com

Copyright © 2010 IDG Communications, Inc.

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