Security Experts:

Locky, Sage Ransomware Share Distribution Infrastructure

Locky ransomware was recently observed being distributed using the same delivery infrastructure previously used to spread the Sage ransomware, PhishMe security researchers warn.

It’s not uncommon for cybercriminals to share infrastructure, so the reuse of the same resources to drop both Sage and Locky isn’t surprising. However, the discovery does show that Locky’s operators are working on securing new distribution venues, after the Necurs botnet, the main Locky distributor, went silent recently.

The Sage ransomware emerged on the threat landscape at the end of 2016 and was detailed early this year. The first delivery emails employed explicit or racy narratives to trick users into opening malicious attachments, but the actors then moved to business-related themes and started using random numbers in email subjects to elude some basic spam filters.

Some of the distribution emails didn’t have a subject line at all, but featured recipient’s name as part of the attachment's file name, which was usually a double-zipped archive containing a malicious Office document or .js file. Other emails claimed to be containing information about a financial transaction that had been rejected, or that a deposit of a refund had been failed after an order had been canceled.

According to PhishMe, the campaign they analyzed leveraged a .zip file (named “document_1.zip”) with a JavaScript application inside, meant to download the Sage ransomware in the form of a Windows executable. The payload was retrieved from the domain affections[.]top, and the malware leveraged the same payment gateway’s Tor site as before, as well as the Tor2Web gateway addresses on er29sl[.]com and rzunt3u2[.]com.

Starting on January 26, 2017, however, a phishing campaign used to deliver the Locky ransomware was observed using the very same email narratives and metadata. Furthermore, the domain affections[.]top was being used as part of the delivery process for this ransomware family 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,” PhishMe notes. The relation between Locky and Kovter has been detailed a few times lately, most recently by Microsoft, which stumbled upon a two-step delivery technique which attempted to drop Locky first, but switched to Kovter if that failed.

The overlapping infrastructure also demonstrates once again how cybercriminals frequently reuse malware support and distribution infrastructure. The distribution of both Sage and Locky from the same location can be seen as evidence of the commodity status for ransomware tools like these. Both malware variants being distributed using these attributes and infrastructure enjoy equal effectiveness, but this also provides researchers and security professionals with a few avenues for mitigating them.

“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,” PhishMe notes.

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