CISA has published a new Malware Analysis Report (MAR) on DarkSide Ransomware and updated Alert AA21-131A: DarkSide Ransomware: Best Practices for Preventing Business Disruption from Ransomware Attacks, originally released May 11, 2021. This update adds indicators of compromise associated with a DarkSide ransomware variant that executes a dynamic-link library used to delete Volume Shadow copies available on the system.

DarkSide is ransomware-as-a-service (RaaS)—the developers of the ransomware receive a share of the proceeds from the cybercriminal actors who deploy it, known as “affiliates.” According to open-source reporting, since August 2020, DarkSide actors have been targeting multiple large, high-revenue organizations, resulting in the encryption and theft of sensitive data. The DarkSide group has publicly stated that they prefer to target organizations that can afford to pay large ransoms instead of hospitals, schools, non-profits, and governments.

According to open-source reporting, DarkSide actors have previously been observed gaining initial access through phishing and exploiting remotely accessible accounts and systems and Virtual Desktop Infrastructure (VDI) (Phishing [T1566], Exploit Public-Facing Application [T1190], External Remote Services [T1133]).[],[] DarkSide actors have also been observed using Remote Desktop Protocol (RDP) to maintain Persistence [TA0003].[]

After gaining access, DarkSide actors deploy DarkSide ransomware to encrypt and steal sensitive data (Data Encrypted for Impact [T1486]). The actors then threaten to publicly release the data if the ransom is not paid.

CISA recommends that users and administrators consider using the following best practices to strengthen the security posture of their organization's systems. Any configuration changes should be reviewed by system owners and administrators prior to implementation to avoid unwanted impacts.

• Maintain up-to-date antivirus signatures and engines.
• Keep operating system patches up-to-date.
• Disable File and Printer sharing services. If these services are required, use strong passwords or Active Directory authentication.
• Restrict users' ability (permissions) to install and run unwanted software applications. Do not add users to the local administrators group unless required.
• Enforce a strong password policy and implement regular password changes.
• Exercise caution when opening e-mail attachments even if the attachment is expected and the sender appears to be known.
• Enable a personal firewall on agency workstations, configured to deny unsolicited connection requests.
• Disable unnecessary services on agency workstations and servers.
• Scan for and remove suspicious e-mail attachments; ensure the scanned attachment is its "true file type" (i.e., the extension matches the file header).
• Monitor users' web browsing habits; restrict access to sites with unfavorable content.
• Exercise caution when using removable media (e.g., USB thumb drives, external drives, CDs, etc.).
• Scan all software downloaded from the Internet prior to executing.
• Maintain situational awareness of the latest threats and implement appropriate Access Control Lists (ACLs).

Additional information on malware incident prevention and handling can be found in National Institute of Standards and Technology (NIST) Special Publication 800-83, "Guide to Malware Incident Prevention & Handling for Desktops and Laptops".

CISA also encourages users and administrators to review the following resources for more information:

• AA21-131A: DarkSide Ransomware: Best Practices for Preventing Business Disruption from Ransomware Attacks
• Malware Analysis Report MAR-10337801-1.v1