Security Experts:

Defray Ransomware Used in Selective Attacks Against Multiple Sectors

A newly discovered ransomware variant has been used in small, selectively targeted attacks aimed at healthcare and education, and manufacturing and technology, respectively.

Dubbed Defray and discovered by Proofpoint earlier this month, the malware appears to have been involved only in two attacks, distributed via Word documents attached to phishing emails. The campaigns consisted of only several messages each, while the lures were specifically crafted for the intended targets.

The Microsoft Word documents carrying the ransomware contain an embedded OLE packager shell object. When the victim opens the document, the malware is dropped in the %TEMP% folder, and a file named taskmgr.exe or explorer.exe is then executed.

Defray contains a hardcoded list of around 120 file extensions to encrypt, though security researchers from Proofpoint noticed that the malware would also encrypt files with extensions that are not on the list (such as .lnk and .exe). The ransomware doesn’t change the extension of the encrypted files, Proofpoint says.

The threat communicates with the command and control server via both HTTP (clear-text) and HTTPS, to send infection information. After completing the encryption process, the malware disables startup recovery and deletes volume shadow copies. On Windows 7, Defray would also monitor and kill running programs such as the Task Manager and browsers.

To inform the victim of what happened with the files, the ransomware creates a ransom note called FILES.TXT in “many folders throughout the system,” along with a file called HELP.txt on the desktop (with identical content).

“The ransom note […] follows a recent trend of fairly high ransom demands; in this case, $5000. However, the actors do provide email addresses so that victims can potentially negotiate a smaller ransom or ask questions, and even go so far as to recommend BitMessage as an alternative for receiving more timely responses. At the same time, they also recommend that organizations maintain offline backups to prevent future infections,” Proofpoint reveals.

To date, the malware was observed only in two distinct attacks, one targeting Manufacturing and Technology verticals, on August 15, and another primarily aimed at Healthcare and Education, on August 22. As part of the first campaign, the emails featured the subject “Order/Quote” and referenced a UK-based aquarium with international locations. In the second campaign, the emails used a UK hospital logo, purporting to be from the Director of Information Management & Technology at the hospital.

“Defray Ransomware is somewhat unusual in its use in small, targeted attacks. Although we are beginning to see a trend of more frequent targeting in ransomware attacks, it still remains less common than large-scale “spray and pray” campaigns. It is also likely that Defray is not for sale, either as a service or as a licensed application like many ransomware strains. Instead, it appears that Defray may be for the personal use of specific threat actors, making its continued distribution in small, targeted attacks more likely,” Proofpoint concludes.

Related: ICS Security Pros Increasingly Concerned About Ransomware: Survey

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