A cybercrime campaign that starts with phishing, uses Bit.ly and Pastebin to pass commands, and results in the theft of the victim's user credentials, cryptocurrency wallets, and web history may have cost as little as $160 to run and likely infected thousands of systems every week, according to two researchers with security firm Prevailion.

The campaign, which the firm calls the MasterMana botnet, keeps costs down by hosting it on a single virtual private server and using public services as drop boxes for documents that contain encrypted commands, according to the firm's October 2 analysis. The attack highlights the asymmetry between attackers and defenders — with a few hundred dollars, attackers can breach defenses that may cost hundreds of thousands or millions of dollars annually, says Danny Adamitis, director of intelligence for Prevailion.

"When it came down to monetary cost, the only thing that these actors were paying for was the $100 for one Trojan and the $60 a month for a virtual private server from one particular provider," Adamitis says. "You can cause so much mayhem for so little money."

While a great deal of industry focus is on opportunistic attacks that could potentially affect hundreds of thousands of systems, or targeted attacks that home in on a few dozen victims, the bargain-basement infrastructure used by MasterMana shows that even small-time attacks can be a worry for companies if they're conducted by relatively skilled attackers, Adamitis says.

In their analysis of the botnet, Prevailion's researchers argued that the balance between sophistication and low-cost techniques hit a sweet spot that many advanced persistent threats (APTs) miss. The attack is "sophisticated enough to avoid automated detection through third-party services and obfuscation, while remaining below APT-level sophistication to avoid drawing attention to their campaign," Adamitis and Adam Flatley, vice president of tailored intelligence, wrote in the analysis.

The attack starts with phishing e-mails requesting information about the targeted company's products. While the e-mail messages are not very well constructed, thousands of victims have apparently opened the attached Microsoft Excel file. If the victim opens the attachment, either a macro will run and connect to Bit.ly or, in another case, the attackers used a vulnerability from 2017. While Prevailion did not see other file formats used in the attack, the company has seen other analyses citing malicious documents in Microsoft's other file formats, including Word, PowerPoint, and Publisher.

The Bit.ly link led to a Blogspot page, which then ran malicious JavaScript code that, in turn, downloaded and ran code from Pastebin. The multiple redirections make it harder to analyze the code and automatically assess whether the application is malicious, Adamitis says. The code created scheduling tasks and modified a registry key, which provides persistence and can download the remote access trojan (RAT).

Using statistics provided by Bit.ly and Pastebin, Adamitis estimated that 2,000 systems interacted with the botnet sites every week. Although that doesn't mean that 2,000 system were infected each week, the number suggests that the activity continues to make the botnet a threat.

"This is one of those attacks that should be threat modeled and you should worry about, because this type of approach is going to affect a large number of people," Adamitis says.

Many attributes of the attack are hallmarks of the Gorgon Group, a Pakistan-affiliated team of cybercriminals, according to Prevailion. The Gorgon Group does not just focus on financial fraud and cybercrime but also conducts attacks against government organizations and has been linked to attacks against Spain, Russia, the United Kingdom, and the United States. The group has used a variety of software tools in the past, including njRAT, QuasarRAT, and Remcos, according to MITRE's ATT&CK framework.

The Prevailion researchers recommend that companies protect their systems with updated security software, firewalls, and some form of attack detection. Both of the initial file-infection vectors — using a macro to install software and exploiting a 2-year-old vulnerability — would be caught by most forms of modern endpoint security.

In addition, properly updated endpoint security software would have stopped the RAT from running, according to the researchers' analysis.

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