Security experts at the SANS Institute Internet Storm Center, discovered that that two malware families, NemucodAES and Kovter are being delivered together in .zip attachments delivered via active spam campaigns.
“By March 2016, we started seeing reports of ‘Nemucod ransomware’ that stopped downloading ransomware binaries in favor of using its own script-based ransomware component,” Duncan wrote in a SANS Institute Internet Storm Center posted Friday.
The NemucodAES ransomware is easy to neutralize due to the availability of a decryptor, meanwhile, Kovter click-fraud is a fileless malware hard to detect. Kovter was also used by threat actors to steal personal information and download and execute additional malicious payloads.
Spam campaigns deliver the malicious .zip archives disguised as notices from the United Parcel Service.
Kovter was packaged with other ransomware in past campaigns, in February, experts at Microsoft’s Malware Protection Center spotted malicious email campaigns using .lnk attachments to spread Locky ransomware and Kovter.
The NemucodAES ransomware encrypt files without appending any info to the original file names, then it delivers in the “AppData\Local\Temp” directory instructions (via an .hta file) to decrypt the files. It also uses a Windows desktop background (a .bmp file) as the ransomware note.
Victims are requested to pay a $1,500 ransom in Bitcoin.
Experts are investigating the presence of the Kovter malware in the campaigns. Kovter seems to be used only to check traffic and generating command-and-control traffic.
“I see a lot of post-infection events for Kovter command and control traffic. But I’m not certain click-fraud is involved any more,” Duncan said.
Give a look at the SANS’s analysis for further details about this campaign.
(Security Affairs – NemucodAES ransomware, spam)