Citadel Malware Brings Service To Cybercrime

When the developers of the popular Zeus banking Trojan released the program's source code last year, many security experts warned Internet users to brace for a deluge of malware. Instead, relatively few variants of the well-known bot software have appeared.

Enter the Citadel malware-as-a-service model. The brainchild of what appears to be Russian and Ukrainian programmers, Citadel is a development effort that aims to provide better support for its offshoot of the Zeus code base, while at the same time allowing clients to vote on feature requests and code their own modules for the crimeware platform. First detected in early December 2011 by threat-management firm Seculert, the platform has gained popularity quite quickly, says Aviv Raff, chief technology officer for the company.

"Currently, we see over 20 different botnets using Citadel," Raff says. "This is huge in terms of fast adoption of a new type of malware."

Like many legitimate software companies, the Citadel project brings easy service via a customer-relationship management portal. The evolution has "explosive potential," Seculert warned in a blog post earlier this month. Already, the project has led to the creation of modules for better encryption, video screen capture, and methods of avoiding detection -- some coded by Citadel developers, other by the project's customers.

While security companies do not expect that the Citadel development model will necessarily result in more elusive malware, breaking down the barriers to using malware through better customer service could mean a wider variety of cybercriminals will start using the software, says Jason Milletary, technical director for malware analysis at security-management firm Dell SecureWorks.

"It is going to potentially put more crimeware into more criminals' hands, which is obviously going to have an impact," Milletary says. "Whenever you have more people providing more alternatives, it is going to spawn innovation."

If Citadel's development model becomes popular, then Milletary expects that other crimeware developers will take notice and offer better customer service as well. "What we see is similar to what we see in legitimate economies," he says.

The result will likely be that the overall quality of malware will become more professional as other writers of viruses and Trojans adopt the model.

Yet not everyone agrees. The addition of better customer service to the toolboxes of malware developers will not necessarily lead to the faster adoption and evolution of the source code, says Vikram Thakur, principal security response manager for security firm Symantec. Relatively few cybercriminals have the technical chops to develop the Zeus code base, and that's unlikely to change.

"I don't think there are many people who will be able to leverage that existing code and be able to continue the services better than what was already in the market," he says.

The addition of support does make it likely that the Citadel project will last longer. Depending on the jurisdiction from which the developers operate, a popular project could make them a bigger target for international law enforcement.

No matter what happens, the evolving development processes in the underground will likely lead to the extinction of the old Zeus source code, Thakur says.

"Right now, perhaps 50 percent of Citadel code is similar to the original code, but in a year's time, that will be down to 30 percent," he says.

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