Attackers behind the Dridex Trojan have narrowed their sights on banks based in the United Kingdom frequented by high-value business accounts, researchers claim.
When a new version of the Trojan was released two weeks ago, it was promptly followed by a series of infection campaigns that focused on UK users.
Limor Kessem, a cybersecurity evangelist at IBM’s X-Force, who published a blog entry about the Trojan’s latest whereabouts on Tuesday, claims the latest chain of infections is leveraging the Andromeda botnet. The Trojan’s operators targeted two banks in the U.K. to start, but within a few days, was targeting 13 banks. That Dridex is targeting U.K. banks is hardly surprising, the malware has long had an affinity for going wherever the money is. Developers behind the Trojan are simply honing in on high-value targets, in this case banks with dedicated subdomains for business and corporate account access, IBM said.
To carry out the attacks, Dridex is tricking victims into opening fake invoices in the form of Microsoft Office files that launch the Trojan via tainted macros. When users click through to their bank’s website, Dridex sends users to a different website than the one they expected, in hopes of gleaning their login, or password with neither the user, nor the bank being any the wiser.
If the tactic sounds familiar, it should – the technique shares a few similarities with how Dyre tricks victims into navigating to redirected, compromised sites. Unlike Dyre, which redirects users via local proxy, Dridex redirects users via local DNS poisoning. Kessem said that while the technique isn’t new, it still involves a lot of prep time.
“To prepare for such a redirection attack, the cybercrime gang needs to invest heavily in creating website replicas of targeted banks,” Kessem wrote, “When Dyre started using this scheme, it was targeting more than a dozen banks — a rather resource-intensive operation that eventually drove Dyre’s operators to switch back to using web injections and page replacements.”
The Dridex team appears to have ramped up its efforts quickly though, prompting Kessem to ponder whether the two groups either share key developers or management, or whether the Dridex team purchased some site replicas from the Dyre group. When we last heard from Dridex in October, the malware was alive and well, tricking French users into opening malicious Microsoft Office files rigged to look like hotel receipts.
That news came just a few weeks after officials with the FBI, the Department of Justice and the UK National Crime Agency reportedly disarmed Dridex by taking down one of the bigger botnets behind it. As the malware continues to wind its way through Europe, it appears the Trojan isn’t dead yet.