Dropbox, WordPress Used As Cloud Cover In New APT Attacks

The cyberespionage gang out of China who recently hacked into media outlet networks is now using Dropbox and WordPress in its attacks rather than via traditional email phishing attacks and server compromise, new research has found.

The so-called DNSCalc gang, which breached The New York Times during the fall of 2012 and again in early 2013, appears to be the culprit behind a new wave of attacks targeting individuals and groups associated with the Association of Southeast Asian Nations (ASEAN) Member Nations. The group's new M.O.: using Dropbox to distribute its malware and WordPress for the initial stage of the command-and-control (C&C).

Adam Vincent, CEO of Cybersquared, which analyzed the attacks and gathered intel via its new ThreatConnect crowdsourcing research service, says this represents a change in tactic that basically better ensures persistence. "This represents a shift from existing methods where attackers leverage their own infrastructure to directly spearphish and interact with their victims. Leveraging trusted cloud infrastructure allowed the attacker to move much faster in the staging and execution of their attack," Vincent says.

He says his team has seen other campaigns using these methods as well. "They are all looking at leveraging existing cloud services as their infrastructure to target the victim and also maintain their access to the victim's network," he says. "They are hiding in the noise of cloud computing."

Exploiting cloud file-hosting services such as Dropbox for distributing malware isn't a new concept. The practice actually began in the late 1990s with shareware distribution sites, notes Gunter Ollmann, CTO at IOActive. "However, with the addition of private file-sharing URLs via these cloud hosting services, it has become a popular vector initiating targeted attacks over the last three to five years," Ollmann says. "The anonymity associated with posting the files and the whitelisting of the servers by enterprise perimeter-filtering technologies combine to make it a convenient tool for hosting the malicious content."

It is unusual to see WordPress sites serving as C&Cs, Ollmann says, because they are often detected by Web scanners and automated malware analysis. Low-volume, targeted attacks via WordPress C&Cs could survive longer than mass-infection attacks, he says. "The use of such public services provides multiple avenues for providing anonymity and making it difficult to attribute to specific criminal operators," he says.

The attackers used a phony U.S.-ASEAN business council memo as one lure, sent via a Dropbox notification. (ASEAN is a nongovernment organization that represents the political and economic interests of 10 Southeast Asian nations). The malicious file was a Word document with embedded malware; once the victim opened the file, the malware reached out to a WordPress blog -- unbeknown to the victim -- that provided commands to reach a secondary domain, IP address, and port number of a second-stage C&C server.

No blatant botnet C&C required, and no need to compromise a Web server or SMTP relay to launch the attack: "In this case, the attacker used Dropbox to distribute the malware and WordPress for first stage command and control," Vincent says.

"The blog appears as a blog for the firewall, so security people won't notice it," Vincent says. "The malware is sucked down that blog page, and the commands tell the malware what to do and where to go next."

The Dropbox account allows the attackers to anonymize themselves behind the account and also use the trusted Dropbox brand to lure the victims into opening the files. And with the cover of Dropbox and the WordPress blog, they could more easily bypass malware detection.

[A group of Taiwanese researchers peer into the operations center of a group behind one large espionage campaign. See Cyberespionage Operators Work In Groups, Process Enormous Data Workloads.]

Exploiting the cloud for attack infrastructure isn't just an APT phenomenon, however. "It's going to be the next step for all sophisticated or advanced threats -- APT or cybercrime," Vincent says. "I think what we have seen has been cyberespionage-focused to date. But now that it's being seen as a success that will help their attacks, it will turn into being more prevalent on the criminal side" as well, he says.

Cybersquared's full blog post, with screenshots of the attacks, is available here.

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