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Cyberspies Resuscitate Citadel Trojan For Petrochemical Attacks

The Citadel Trojan is a rare and odd choice of malware for cyber espionage purposes, experts say.

A newly discovered cyberspying campaign targeting petrochemical firms in the Middle East has security researchers baffled over its use of a variant of the old banking Trojan Citadel.

IBM Trusteer researchers recently found evidence of the attacks, which targeted one of the largest petrochemical product companies in the Middle East, a raw petrochemical materials supplier in the region, and other victims which IBM would not name.

Dana Tamir, director of enterprise security at Trusteer, an IBM company, says this was the first time her team had seen Citadel used in a cyberspying operation for stealing corporate information or accessing corporate email servers. Citadel, which was built for stealing banking credentials, typically using man-in-the middle browser attacks, is no longer supported and upgraded by its author.

"APTs in the past used highly customized malware and delivery. This is no longer the case. These Trojans are already massively distributed," Tamir says. One in 500 machines worldwide is infected with this type of "massively distributed" malware at any time, according to IBM Trusteer's data.

Tamir says the team doesn't know how the attackers first infected the machines. The command and control server had already been taken offline by the time her team got access to the configuration file. "We don't know who's behind it or which region it was coming from."

With mainstream financial Trojans like Citadel being used for cyber espionage, the attackers can cast a wider net with the malware and merely filter out the desired targets. "On the one hand, it's opportunistic," where the attackers filter out the infected victims of the industries or companies on which they want to spy. "But they are very targeted in the configuration file specifically. If they see a machine that belongs to these targets," they start stealing the information they want.

"This massively distributed malware means they don't need sophisticated ways to attack" their targets, Tamir says. Banking Trojans make infections more efficient and don't require the attackers to have significant intelligence up front about their targets.

In the Citadel-based attack, the malware looks for certain URL addresses of webmail for the targeted firms, for instance, and it intercepts the infected user's HTTP POST data, including login credentials to webmail.  That gives the attackers instant inside access to the target.

[At least two different cyber espionage gangs in China appear to be employing uniform tools and techniques. Read Franchising The Chinese APT.]

Cyber espionage gangs have been evolving toward more efficient and streamlined attacks. FireEye recently revealed that two Chinese APT gangs known for targeting very different industries were recently spotted using some of the same or similar tactics, tools, and resources. Researchers at AlienVault Labs have seen different Chinese APTs sharing zero-day exploits, for example.

Dmitri Alperovitch, co-founder and CTO of CrowdStrike, says his team also has never seen Citadel used in a cyber espionage campaign before. Citadel, which is no longer being supported by its authors, seems a bizarre option, since it's not the best way to avoid detection. "It's not the best tool you want to use in avoiding detection. Zeus would have been much better," mainly because it continues to get updated features for evading detection.

"The fact that they used Citadel when it's obsolete tells me either they don't know what they are doing" or the attackers aren't very experienced, he says.

Alperovitch doubts the attackers came out of Iran, because most Iranian APTs are now creating their own custom malware.

The big thing CrowdStrike is seeing are Chinese APT groups moving away from using malware in their exfiltration phase. "They want to avoid being noisy, so they typically break in and steal credentials so they have access in the network and operate as insiders."

They still have to use some form of malware to steal credentials, of course, but the actual spying and stealing is executed manually.

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