Digital stakeout of Chinese hacker gang reveals 100+ victims

Crew behind 'Comfoo' RAT may have rooted through videoconferencing vendor for ways to watch confidential meetings in government, businesses

A Chinese hacker gang whose malware targeted RSA in 2011 infiltrated more than 100 companies and organizations, and was so eager to steal data that it probed a major teleconference developer to find new ways to spy on corporations, according to researchers.

The remote-access Trojan, or RAT, tagged as "Comfoo" is largely inactive, said a pair of veteran researchers from Dell SecureWorks, who presented their findings at last week's Black Hat security conference.

But their discoveries showed just how pervasively a dedicated group of attackers can infiltrate networks and walk away with secrets.

"We're not seeing it used to the extent it was before," said Joe Stewart, director of malware research at SecureWorks, in explaining why he and his college, Don Jackson, revealed their undercover campaign.

For more than 18 months, Stewart and Jackson, director of SecureWorks' Counter Threat Unit (CTU), secretly monitored some of the workings of Comfoo, which they believe was the work of a hacker crew they've named the Beijing Group. The gang is one of China's top-two hacker organizations.

To start, Stewart captured a sample of the malware used in the RSA attack, at the time attributed to Chinese hackers, then reverse-engineered the encryption that the malware used to mask instructions to and from the gang's command-and-control (C&C) servers.

Eventually, Stewart was able to spy on the hackers as they logged onto those C&C servers. As they did, Stewart snatched the victims' MAC addresses -- unique identifiers for network hardware -- their IP, or "Internet protocol" addresses, and finally, a tag the hackers used to label each data-stealing campaign.

SecureWorks was not able to see what data the attackers were stealing, but their passive monitoring reaped dividends.

"We've done similar ops like this before," said Stewart, "but with the custom stuff, you rarely get this kind of insight or this level of detail of the attacks and victims."

SecureWorks said its stealthy stakeout -- which was intermittent to ensure that the hackers weren't aware they were watching -- uncovered over 100 victims, more than 64 different campaigns and 200-plus Comfoo variants. The Atlanta-based security firm notified some of the victims directly, and others through CERTs, the computer emergency response teams that governments maintain.

"This was just a snapshot of the [total] victims," cautioned Stewart.

The hackers targeted a wide range of government agencies and ministries, private companies and trade organizations in fields as diverse as energy, media, semiconductors and telecommunications. They seemed eager to grab information from almost anywhere and anyone, although the victims were concentrated in Japan, India, South Korea and the U.S.

SecureWorks' virtual stakeout pinpointed the physical location of many of the Comfoo C&C servers. China was the hotspot. (Image: SecureWorks.)

But one victim caught their attention.

While Stewart and Jackson declined to name any of the victims, they said one campaign had been aimed at a major videoconferencing software developer.

They speculated that the attackers were sniffing through that company's network for information on vulnerabilities in the software, which they could then exploit at other targets to put eyes and ears on confidential industry and government meetings. "They might be trying to leverage that access to spy on third parties," said Stewart.

In a report SecureWorks published last week on Comfoo, the company said that targeting audio and videoconferencing products was "unusual."

Other attacks may have had the same goal: Acquire inside information on everything from specialized security software to digital certificates for use in future campaigns.

SecureWorks' surveillance will also let security researchers better track the hacker gang, even though the cyber criminals have changed their malware tools since using Comfoo, and will undoubtedly do so again, said Jackson.

"It's safe to assume that they'll change their toolkits," Jackson said. "But as long as the key features match, we should be able to match them [in the future] with campaigns."

Hacker gangs, Jackson added, have personalities and quirks, and can be "fingerprinted" by closely analyzing not only the malware they use, but also how they organize the C&C infrastructure. "They all have patterns," Jackson said.

Although he wouldn't go into specifics, Jackson said that SecureWorks had already used the patterns found in the Comfoo campaigns to identify newer malware and attacks that the company believes is the work of the Beijing Group.

"As long as it's evolutionary rather than revolutionary, we should be able to spot them," Jackson said.

More information about the Comfoo surveillance can be found on SecureWorks' website.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is

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Copyright © 2013 IDG Communications, Inc.

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