A new iteration of the backdoor Trojan Makadocs is capable of hiding its command-and-control (C&C) server communications by abusing a legitimate Google Docs function.
According to Symantec researchers, the malware is using Google Docs as a proxy server to pass along information to C&C servers. The tweaked code is also capable of comprising machines running Microsoft's Windows 8 and Windows Server 2012.
Kevin Haley, director of product management within Symantec security response, told SC Magazine US that fewer than 100 Makadocs infections have been detected, and he believed that the individuals behind the malware apparently were just testing out the updated malware.
Makadocs, which is downloaded on victims' machines when they open malicious Word or Rich Text Format (RTF) documents sent in phishing emails, uses legitimate functionality within Google Docs to hide its communications.
“There's a feature in Google Docs called ‘viewer' that allows you to look at a document on another person's machine. You can get the URL of where the document is [through the feature]. Makadocs can use the ‘viewer' feature to access its C&C server instead,” he said.
While the phishing tactics used to spread the Trojan are commonplace, what Makadocs creators developed to keep the C&C communications under the radar is what caught researchers' attention.
Since the malware existed before Windows 8 was launched, researchers believe the code was updated after the operating system was introduced to widen its threat to users.
He said: “The malware is built to steal information from the computer, so it's a pretty standard information stealer.” He also said that basic information such as the infected computers' domain name and operating system of choice were passed along to C&C servers.
Symantec also said that it was possible for Google to thwart this abusive behaviour by blocking the malware's connection to the Docs server using a firewall. A Google spokesman said that the company would take action if abuse of its services became a major concern.