Nokoyawa Ransomware: In-Depth Analysis, Detection, and Mitigation
Summary of Nokoyawa Ransomware
The Nokoyawa is a ransomware family first discovered in February 2022 that has since been rewritten in the Rust programming language. It utilizes Elliptic Curve Cryptography (ECC) with SECT233R1 and Curve25519 and Salsa20 for file encryption and runtime flexibility via a command-line configuration parameter. Nokoyawa is an evolution of the Nemty and Karma ransomware families. The authors of Nokoyawa utilized (direct code-reuse) many functions from the leaked Babuk source code. Nokoyawa practices a double extortion technique, demanding payment for a decryptor and the non-release of stolen data. It is delivered via a third-party framework (aka Cobalt Strike) and phishing emails, and its authors have reused functions from the leaked Babuk source code. Nokoyawa ransomware can exfiltrate sensitive data from organizations and encrypt users’ files. Its operators have a limited command set that grants them fine control over the execution and outcome of the infection.
What Does Nokoyawa Ransomware Target?
Nokoyawa ransomware generally targets businesses and organizations, particularly those in the healthcare, financial services, government, and manufacturing sectors.
How Does Nokoyawa Ransomware Spread?
Nokoyawa can be delivered via Cobalt Strike or similar frameworks, as well as through email phishing. Nokoyawa operators are known to employ Commercial off the Shelf Tools (COTS) to explore and expand within infected environments. These tools include PC Hunter and GMER.
Nokoyawa Ransomware Technical Details
Nokoyawa is an evolution of the Karma and Nemty ransomware families. Similar to its predecessors, Nokoyawa accepts certain command-line parameters during operation. These include options to toggle network spreading as well as the ability to only encrypt specific files or paths.
There are minor differences between Karma and Nokoyawa with regards to how individual file encryption is accomplished. Both Nokoyawa and Karma variants dynamically load bcrypt.dll and call BCryptGenRandom to generate 0x20 random bytes. They generate an ephemeral Sect233r1 key pair using the generated random bytes as the seed. The malware then uses the private ephemeral key and the public embedded key to generate a shared Salsa20 key, which is subsequently used for the file encryption. The Salsa20 nonce is hardcoded as “lvcelvce” in Nokoyawa, whereas in the Karma version it was “11111111”.
Nokoyawa uses multi-threading to quickly and efficiently encrypt files, skipping some extensions in the process. Each encrypted file has a “.NOKOYAWA” extension added to it, and a ransomware note called “NOKOYAWA_readme.txt” is dropped into each folder with both an English and Chinese version.
How to Detect Nokoyawa Ransomware
- The SentinelOne Singularity XDR Platform can identify and stop any malicious activities and items related to Nokoyawa.
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:
- 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.
- Monitor network traffic and look for indicators of compromise, such as unusual network traffic patterns or communication with known command-and-control servers.
- Conduct regular security audits and assessments to identify network and system vulnerabilities and ensure that all security controls are in place and functioning properly.
- Educate and train employees on cybersecurity best practices, including identifying and reporting suspicious emails or other threats.
- 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 Nokoyawa Ransomware
- The SentinelOne Singularity XDR Platform can return systems to their original state using either the Repair or Rollback feature.
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In case you do not have SentinelOne deployed, there are several steps that organizations can take to mitigate the risk of ransomware attacks:
- 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.
- 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.
- 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.
- 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.