Pierluigi Paganini February 07, 2017

PhishMe security researchers discovered that the Locky and Sage ransomware were recently observed being distributed by the same delivery infrastructure.

It’s a common habit of cyber criminals to share delivery infrastructure to maximize the use of their resource and minimize the cost,

Recently the Locky ransomware was observed being distributed through the delivery infrastructure used to spread the Sage ransomware.

A couple of weeks ago, researchers from the Cisco Security Team has noticed traces of traffic from the dormant Necurs botnet and warned of a possible new massive ransomware spam campaign.

Now researchers at Phishme, reported cybercriminals are sharing the delivery infrastructure for both Sage and Locky, likely because operators behind the Locky threat are working on securing new distribution channels, after the Necurs botnet, the main driver behind the Locky and Dridex activity, slightly vanished.

“Sage and Locky Ransomware Now Sharing Delivery Infrastructure in Phishing Attacks” titled a blog post published by Phishme.

The Sage ransomware was recently emerged, the malware researchers spotted in December 2016, it was spread through phishing messages using malicious attachments. Threat actors frequently changed tactic to elude spam filters, for example, they used in the recent campaigns random numbers in email subjects.

“Following this early distribution, threat actors moved toward the mainstream in a major way. The phishing email subjects used random numbers to help elude some basic filters and leveraged business-related themes rather than explicit or racy narratives.  The body of these emails explained that a financial transaction had been rejected and claimed that details about the failure could be found an attached document.” reads the analysis published by Phishme.

Some of the distribution emails didn’t have a subject line and used recipient’s name as part of the attachment’s file name. The attachment is a double-zipped archive containing a malicious Office document or .js file that is used to launch the attack.

Some emails claimed to be containing information about a financial transaction that had been rejected, or that a deposit of a refund had been failed due to the cancellation of an order.

“In this more polished campaign, the .zip file (named “document_1.zip”) contained a JavaScript application which, when run, facilitated the download of a Windows executable representing the Sage Ransomware to be downloaded.” continues PhishMe.”In this case, the payload binary was retrieved from the domain affections[.]top, however the payment gateway’s Tor site, as well as the unusual Tor2Web gateway addresses on er29sl[.]com and rzunt3u2[.]com remained the same.” 

Starting on January 26, 2017, the experts noticed a phishing campaign used to deliver the Locky ransomware with many similarities with a campaign used to spread the Sage ransomware. The researcher observed the use of the domain affections[.]top as part of the delivery infrastructure on Monday, January 30.

“This connection pushes the narrative forward in yet another way as the Locky distribution in question was yet another example of that ransomware being paired with the Kovter Trojan,” continues PhishMe notes.

Researchers at Microsoft demonstrated on the past the link between Locky and Kovter threats, they detailed a technique adopted by crooks which first attempted to drop Locky ransomware, but that switched to Kovter malware in case of failure.

The distribution of both the two threats, Sage and Locky, from the same delivery infrastructure let the experts in to believe that operators were likely using a service offered in the criminal underground to spread the ransomware.

“First, the shared infrastructure provides a high-fidelity indicator of compromise that can be preemptively blocked to foil the delivery of multiple ransomware varieties. Secondly, since the qualitative tactics, techniques, and procedures used in the distribution of these ransomware varieties are nearly identical and closely resemble classic phishing narratives easily recognizable to users prepared and empowered to identify and report phishing emails,” added PhishMe.

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Pierluigi Paganini

(Security Affairs – Locky, ransomware)