An old-school banking Trojan has been reincarnated as a weaponized document payload that first steals passwords and then drops ransomware.

The Betabot Trojan, which the FBI warned about in 2013, is best known as a botnet and for disabling anti-malware software and bypassing virtual machines and sandboxes on victim machines in its quest to steal passwords. But researchers at Invincea have discovered Betabot spreading via rigged documents: after it steals a victim’s browser-stored passwords, it then drops the infamous Cerber ransomware in a second phase of the attack.

Invincea says this is a first: a weaponized document that steals passwords then uses ransomware on its victims.

Patrick Belcher, senior director of threat research at Invincea, says Betabot has infected thousands of victims in this latest iteration. “We haven’t seen Betabot ever do this: doing a phishing run with the same sort of phishing Cerber was using. Instead of using just Cerber, the [attackers] are installing Betabot and then going to Cerber.”

Cerber is a ransomware tool that has caught fire in the cybercrime underground. It uses a ransomware-as-a-service model, which allows nontechnical criminals to deploy it. Cerber affiliates extorted from their victims some $195,000 in July, according to recent data from Check Point, and Cerber’s author nets around $946,000 per year, a hefty income for ransomware operations.

Why the one-two punch? Belcher says it’s all about maximizing potential profit. Once the attackers have stolen the stored passwords, they then hit the victim with Cerber ransomware in order to squeeze as much as they can out of an infected victim.

“They were really after the passwords, I think, or they would not bother to drop Betabot. But they are trying to maximize their profits for each compromised endpoint. They get an amount of value on passwords of the systems … and the second whammy is ‘pay ransom’ on top of that,” he says.

Betabot basically harvests any credentials stored in the browser cache, and in the recent campaign, infects users with a malicious macro in a Word Document posing as a resume. The user only gets infected if macros are enabled in the document either by default or manually.

Bottom line: enterprises continue to be juicy marks for phishing lures. “Our research shows that weaponized documents are six times more prevalent than running into an exploit kit,” Belcher says. Not just malicious macros, but otherwise rigged files as well, he says.

“Every business in America is being run having to open up invoices, resumes, documents, reservations … Phishing campaigns have proven to be extremely accurate in the way they are worded,” for example, he says.

Another perplexing issue, notes Belcher: if users are creating strong passwords and then storing them in their browser cache, their passwords are toast in Betabot-type password-stealing attack.

The best bet to protect against this latest Betabot-Cerber campaign—aside from practicing savvy phishing awareness--is to disable macros altogether and for users to refrain from storing any passwords.

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