New Jaff Ransomware Distributed via Necurs Botnet

A brand new ransomware family is being distributed via Necurs, the botnet behind Locky and Dridex campaigns over the past year.

Responsible for an increase in spam-driven malware distribution last year and the main source of Locky infections, Necurs was silent for the first three months of 2017. At the end of March, however, the botnet resumed activity, yet it returned to pushing Locky only in late April.

Dubbed Jaff, the new ransomware variant is using .PDF files as attachments in the spam emails sent by Necurs, the same as Locky did when it resumed activity last month. When opened, the PDF would execute a Word document containing a malicious macro.

In addition to using the same infection vector as Locky, Jaff features a similar payment page too, but appears to be using a different code base. However, the new ransomware is supposedly operated by the same actors that are behind Locky Affid=3 and Dridex 220/7200/7500, Proofpoint security reasearchers say.

Last year, the same threat group released Bart ransomware, a Locky variant that didn’t require connection to a command and control (C&C) server to encrypt victim’s files.

The newly discovered malware is demanding a huge ransom, at around 2 Bitcoin, which tops $3,000 at the time of writing. Most ransomware usually asks users to pay around 0.2 Bitcoin to restore the encrypted data. The recently observed Sage 2.0, however, was demanding a $2,000 ransom.

Jaff currently targets over 400 file types and appends the .jaff extension to the encrypted ones. After the encryption process has been completed, the ransomware drops two ransom notes, named ReadMe.bmp and ReadMe.html.

Distributed via Necurs, the ransomware is likely to hit a large number of users, provided that the group behind it will continue to use it instead of Locky. Primarily focused on the distribution of Dridex and Locky, the actor regularly switches to new document types, lures, exploits, and other methods that help delivering malicious payloads more effectively.

“Similarly, after months of distributing Dridex in high-volume campaigns, they introduced Locky ransomware, which ultimately became the primary payload in the largest campaigns we have ever observed. Within months, they also brought Bart ransomware to the scene. While Bart never gained significant traction, the appearance of Jaff ransomware from the same group bears watching,” Proofpoint notes.

Related: Locky Ransomware Returns in New Necurs-driven Campaign

Related: Dridex Attacks Exploit Recent Office 0-Day

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Ionut Arghire is an international correspondent for SecurityWeek.

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