Grief Ransomware

Introduction: Grief ransomware, also known as PayOrGrief, surfaced in May 2021 as a threat to corporate networks. Engaging in multi-extortion, it demands payment for decryption tools and the non-release of stolen data. It is an evolutionary iteration of the DoppelPaymer/BitPaymer ransomware families.
Targets: Grief ransomware primarily focuses on healthcare, financial services, entertainment, government, and education sectors. Limited targeting of small to medium-sized businesses (SMBs) has been observed.
Propagation: Grief ransomware deploys through Cobalt Strike or similar frameworks, as well as via email phishing. Brute force attacks against Remote Desktop Protocol (RDP) services are also employed in Grief campaigns.
Technical Details:

Payload Evolution: Grief ransomware payloads are an evolution of the Dopplepaymer family with similar functionality.
Initiation: Grief campaigns start with RDP brute-force attacks or phishing/spear-phishing emails.
Phishing Attack: In a phishing attack, a targeted user receives a malicious email leading to the download of an encoded text file containing additional commands and instructions.
Infection Process: Once infected, Grief conducts exfiltration, lateral movement, and eventually deploys ransomware.
Tool Usage: Grief operators adeptly utilize Commercial off the Shelf (COTS) tools and Living off the Land (LOLBins) for internal reconnaissance and traversal.
Encryption: RSA-2048 and AES-256 are used for file encryption, while internal string encryption is handled via RSA-2048 and AES-256 with an RC4 key length of 48 bytes.

Detection Strategies: EDR is effective in identifying and preventing malicious activities related to Grief ransomware. For those without this platform, a multi-layered approach is recommended:

Security Tools: Utilize anti-malware software or security tools capable of detecting and blocking known ransomware variants using signatures, heuristics, or machine learning algorithms.
Network Traffic Monitoring: Regularly monitor network traffic to identify indicators of compromise, such as unusual patterns or communication with known command-and-control servers.
Security Audits: Conduct periodic security audits and assessments to identify vulnerabilities in the network and ensure that all security controls are effective.
Education & Training: Educate and train employees on cybersecurity best practices, emphasizing the identification and reporting of suspicious emails and other threats.
Backup & Recovery Planning: Implement a robust backup and recovery plan to restore data in case of an attack.

Mitigation Measures: For EDR customers, the EDR can return systems to their original state using either the Repair or Rollback feature. For those without EDR , the following steps can help mitigate the risk of Grief ransomware attacks:

Employee Education: Train employees on ransomware risks, phishing email identification, and the avoidance of malicious attachments.
Strong Passwords: Implement strong, unique passwords for user accounts, regularly updating and rotating them.
Multi-Factor Authentication (MFA): Enable MFA for user accounts to add an extra layer of security.
System Updates and Patching: Regularly update and patch systems to fix vulnerabilities and prevent exploitation.
Backup and Disaster Recovery (BDR): Establish regular BDR processes, testing backups stored offsite for quick recovery.

A comprehensive approach, combining preventive measures, employee education, and recovery strategies, is crucial for effectively mitigating the risk of Grief ransomware attacks.

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