Scarab is a strain of ransomware, first spotted in June by the security researcher Michael Gillespie, that is now being distributed to millions of users via a massive spam campaign powered with the dreaded Necurs botnet.
Security researchers believe that Necurs botnet was rented by a threat actor to spread the Scarab ransomware.
The ongoing spam campaign started on concurrently the Thanksgiving, most of the experts in the security community reporting the ongoing spam campaign, including security firms F-Secure and Forcepoint,
Forcepoint experts highlighted huge volume of spam emails sent in a few hours, 12.5 million emails.
“Forcepoint Security Labs have observed another piece of ransomware called “Scarab” being pushed by the infamous Necurs botnet. The massive email campaign started at approximately 07:30 UTC and is active as of 13:30 today, totalling over 12.5 million emails captured so far.” reads the analysis published by Forcepoint.
Necurs now spreading Scarab (https://t.co/M8YD8SS98p).
Let's see if it will be more successful than Locky in past months…@BleepinComputer @demonslay335
cc @MalwareTechBlog pic.twitter.com/e9rPiem9BX
— MalwareHunterTeam (@malwrhunterteam) November 23, 2017
“Necurs’ spam botnet business is doing well as it is seemingly acquiring new customers. The Necurs botnet is the biggest deliverer of spam with 5 to 6 million infected hosts online monthly, and is responsible for the biggest single malware spam campaigns. Its service model provides the whole infection chain: from spam emails with malicious malware downloader attachments, to hosting the payloads on compromised websites.” reported F-Secure.
“The final payload (to our surprise) was Scarab ransomware, which we haven’t seen previously delivered in massive spam campaigns. Scarab ransomware is a relatively new ransomware variant first observed last June, and its code is based on the open source “ransomware proof-of-concept” called HiddenTear.”
The Necurs botnet pushed tens of millions of spam emails of the Scarab ransomware.
According to Forcepoint, by noon, Necurs had already sent out 12.5 million emails carrying what appeared to be a new version of the Scarab ransomware.
The massive Scarab ransomware campaign is evident also from data from the ID-Ransomware service that allows users to detect the type of ransomware that infected their system. The following graph shows the number of submissions for the Scarab ransomware per day.
Scarab emails disguised as archives carrying scanned images, email subjects are chose to trick victims into opening the archive, some of the most popular subject lines used in the campaign were:
Scanned from Lexmark
Scanned from HP
Scanned from Canon
Scanned from Epson
These emails carried a 7Zip archive that contained a Visual Basic script that act as a dropper of the Scarab ransomware.
A first variant of the Scarab ransomware was discovered in June, in July the Malwarebytes researcher Marcelo Rivera spotted a second version that used the “.scorpio” extension.
— Marcelo Rivero (@MarceloRivero) July 10, 2017
The variant currently used by crooks appends the “.[email@example.com].scarab” extension to the original filenames of encrypted files.
The Scarab ransomware deletes shadow volume copies to make impossible to recovery the files, the malware drops a ransom note named “IF YOU WANT TO GET ALL YOUR FILES BACK, PLEASE READ THIS.TXT” on victims’ PCs.
The ransom does refer the ransom sum to pay, but urges victims to contact the Scarab authors via email or BitMessage as soon as possible to pay the smaller the ransom sum.
(Security Affairs – Scarab Ransomware, Necurs botnet)