Onyx: In-Depth Analysis, Detection, and Mitigation

Summary of Onyx Ransomware

Onyx is a type of ransomware, derived from the Chaos builder toolkit, which has been sold and promoted in criminal networks for some time. First spotted in early 2022, Onyx is an improved version of Chaos Ransomware and is similar to Yashma, another version of Chaos Ransomware. One of Onyx’s distinguishing features is that it destroys files instead of encrypting them in a way that can be decoded.  Note, in late 2022, Onyx updated their name (as displayed on their blog) to “VSOP”.

Onyx Ransomware

What Does Onyx Ransomware Target?

Onyx targets SMBs as well as businesses in the healthcare, financial services, education, and government sectors.

How Does Onyx Ransomware Spread?

Payloads are generally delivered via phishing email or a third-party framework (e.g, Empire, Metasploit, Cobalt Strike).

Onyx Ransomware Technical Details

Onyx is written in .NET and based on the output of the Chaos ransomware builder.

Onyx practices double extortion – demanding payment for a decryptor, as well as for the non-release of stolen data. Actors behind Onyx maintain a blog where victims are named and their data is posted should they fail to comply with the demands of the attacker (aka the ransom).  Paths and files subject to encryption are all hard-coded within the Onyx payloads.  Onyx achieves persistence via entries in the registry as well as by dropping a shortcut to the payload in the Startup folder.

Onyx makes a clear distinction for files larger than 2MB. These files are destroyed by overwriting them with random data, making them irrecoverable. Builders of Onyx payloads have access to all the basic options in the Chaos builder platform. Malware authors can customize elements such as the ransom note text, file extensions, encrypted files, process and mutex names, execution delays, and network spreading. There are also more advanced options to make recovery harder, like deleting shadow copies and backup catalogs, and disabling Windows recovery mode. It is also possible to switch away from the standard AES/RSA encryption mode and opt for a more destructive method of simply overwriting all files.

How to Detect Onyx Ransomware

  • The SentinelOne Singularity XDR Platform can identify and stop any malicious activities and items related to Onyx.

In case you do not have SentinelOne deployed, detecting ransomware requires a combination of technical and operational measures designed to identify and flag suspicious activity on the network. This allows the organization to take appropriate action, and to prevent or mitigate the impact of the ransomware attack.

To mitigate the risk of this Ransomware without SentinelOne deployed, it is important to take a multi-layered approach, which includes the following steps:

  1. Use anti-malware software or other security tools capable of detecting and blocking known ransomware variants. These tools may use signatures, heuristics, or machine learning algorithms, to identify and block suspicious files or activities.
  2. Monitor network traffic and look for indicators of compromise, such as unusual network traffic patterns or communication with known command-and-control servers.
  3. Conduct regular security audits and assessments to identify network and system vulnerabilities and ensure that all security controls are in place and functioning properly.
  4. Educate and train employees on cybersecurity best practices, including identifying and reporting suspicious emails or other threats.
  5. Implement a robust backup and recovery plan to ensure that the organization has a copy of its data and can restore it in case of an attack.

How to Mitigate Onyx Ransomware

  • The SentinelOne Singularity XDR Platform can return systems to their original state using either the Repair or Rollback feature.

In case you do not have SentinelOne deployed, there are several steps that organizations can take to mitigate the risk of ransomware attacks:

  1. Educate employees: Employees should be educated on the risks of ransomware, and on how to identify and avoid phishing emails, malicious attachments, and other threats. They should be encouraged to report suspicious emails or attachments, and to avoid opening them, or clicking on links or buttons in them.
  2. Implement strong passwords: Organizations should implement strong, unique passwords for all user accounts, and should regularly update and rotate these passwords. Passwords should be at least 8 characters long, and should include a combination of uppercase and lowercase letters, numbers, and special characters.
  3. Enable multi-factor authentication: Organizations should enable multi-factor authentication (MFA) for all user accounts, to provide an additional layer of security. This can be done through the use of mobile apps, such as Google Authenticator or Microsoft Authenticator, or through the use of physical tokens or smart cards.
  4. Update and patch systems: Organizations should regularly update and patch their systems, to fix any known vulnerabilities, and to prevent attackers from exploiting them. This includes updating the operating system, applications, and firmware on all devices, as well as disabling any unnecessary or unused services or protocols.

Implement backup and disaster recovery: Organizations should implement regular backup and disaster recovery (BDR) processes, to ensure that they can recover from ransomware attacks, or other disasters. This includes creating regular backups of all data and systems, and storing these backups in a secure, offsite location. The backups should be tested regularly, to ensure that they are working, and that they can be restored quickly and easily.

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