Once broken by law enforcement almost a year ago, the Ramnit botnet is now back, researchers said.
A new variant of the Ramnit Trojan and a new botnet that relies on a different command and control (C&C) infrastructure than its predecessor, said researchers at IBM Security.
More than half of current infections were in Canada, followed by Australia, the United States and Finland. However, researchers believe the bad guys will soon expand operations to other countries.
The source code and behavior of the new Ramnit version analyzed by IBM researchers are similar to older variants. However, the malware now relies on much shorter configuration files and uses web injections leveraged by several other Trojans, including Dridex, Shifu and Neverquest.
Researchers said the bad guys might have acquired the web injection mechanism from a group that provides web injections as a service. The content injected into banking websites by the malware now ends up obtained in real time from a remote server.
Ramnit is mostly distributed via malvertising campaigns through the Angler exploit kit, but experts pointed out this is likely not the only infection vector — spam and Ramnit’s worm capabilities ended up used in the past for distribution.
IBM researchers said before it ended up distrupted Ramnit one group owned and operated the botnet, which never sold or shared the source code.
“From what we’ve learned so far, nothing seems to point to a notable change in terms of who is behind Ramnit. It is possible that a new gang has picked the project up, but attribution remains vague in this case,” said Limor Kessem, cyber intelligence expert at IBM Trusteer, in a blog post.
Ramnit first emerged in 2010 as a worm. The next year, its developers used the leaked Zeus source code to turn it into a Trojan designed to steal banking information. In 2014, IBM said the threat was the fourth most active banking malware.
Before it law enforcement disrupted it earlier this year, the Trojan mainly targeted the U.S., the UK and Australia. Its operators also targeted job websites in an effort to recruit mules that could help them obtain stolen money without exposing themselves to law enforcement.
Europol reported after the Ramnit takedown the Trojan had infected over 3.2 million computers.