Symantec researchers have uncovered a Trojan using a private newsgroup within Google Groups as a command and control server. The move follows an attempt to use Twitter as a C&C earlier this year.
Symantec has uncovered a
scheme to use a Google Groups newsgroup to sneak commands to malware
on compromised computers.
The move is another
example of attackers looking for covert ways to communicate to their bots.
Earlier this year, attackers were found using Twitter
as a command and control
(C&C) mechanism. By integrating their messages
with legitimate communications, attackers make it more difficult to identify
and shut down their C&C, according to Symantec.
"This technique is
analogous to the use of encoding messages in newspaper ads that were
commonplace in spy novels," Zulfikar Ramzan, technical director of Symantec
Security Response, told eWEEK. "What attackers are taking advantage of are
online mediums that allow pretty much anyone to post content and are both
highly available as well as readily accessible from the outside. I believe
they are going down this route, since it represents a very easy and
inexpensive avenue for setting up command and control."
In this case, the
attackers infect users with a Trojan Symantec calls Trojan.Grups
The malware targets Windows systems and installs a backdoor on infected
machines. When it's run, it logs into a private newsgroup on Google Groups and
reads a message on the newsgroup that contains the commands to be carried out.
Afterward it posts a response to the newsgroup stating whether the command was
successfully executed or not.
"One noteworthy aspect of
this attack is the use of the RC4 stream cipher to encrypt the messages being
passed back and forth," Ramzan explained. "While encrypting communication is a
conceptually simple thing to do, it demonstrates that attackers are trying to
take extra measures to avoid detection and also to potentially avoid having
their botnet overtaken by some other rogue party."
The method has some
drawbacks for the attacker, however, as every response is stored as a posting
in the newsgroup, making it possible to backtrack the Trojan's activity in
detail. Symantec researcher Gavin O. Gorman speculated that given the
relatively low amount of activity by the Trojan-some 3,000 newsgroup posts
since November 2008-and an examination of its code, this may be a prototype
implementation to test the Web-based newsgroups as C&Cs.
"It is most likely
Taiwanese-based since the newsgroup language is Chinese [simplified], with
several references to .tw domains in commands," Gorman
. "The low numbers imply this is a discreet Trojan, used to subtly
gather information and potentially determine future attack targets. In
addition, there is no attempt within the DLL to maintain persistence on the
attacked computer, further evidence of a Trojan attempting to remain
undiscovered. Such a Trojan could potentially have been developed for targeted
corporate espionage where anonymity and discretion are priorities."
By going this route,
attackers don't have to incur the costs of setting up an explicit
command and control server
, Ramzan added.
"I expect that we'll
continue to see these types of attacks, and that attackers will develop more
refined approaches as sites like Google and Twitter develop better detection
and containment mechanisms," he said.