Dealing with Ransomware

 If a ransomware attack has occurred and you're uncertain about the extent of data and backup corruption or encryption, it's critical to have a structured approach to assess and contain the damage, recover unencrypted data, and prevent further harm. Here's a step-by-step strategy to deal with this situation:

1. Containment

• Isolate Infected Systems: Immediately isolate any systems that are suspected of being compromised to prevent the ransomware from spreading further across the network. This can include disconnecting systems from the network, disabling network shares, and restricting access to storage accounts.
• Disable Network Access: Restrict network access for all compromised accounts and systems, including administrative accounts, to prevent lateral movement by the attacker.
• Stop Backup Jobs Temporarily: Temporarily halt all automated backup jobs until you can verify the integrity of the backup systems and data. You don’t want to overwrite healthy backups with corrupted or encrypted data.

2. Incident Assessment

• Assess the Scope of the Attack: Determine which systems and data have been affected. Check event logs, file changes, and alerts from security systems such as Microsoft Defender for Endpoint, Azure Security Center, and Azure Sentinel to trace the origin and spread of the attack.
• Identify Encrypted Files: Use ransomware identification tools (e.g., CryptoSearch, NoMoreRansom) to scan for file extensions or patterns related to encryption. Also, check for file encryption on critical systems and network shares.
• Verify Backup Integrity: Check the integrity of your backups by comparing the last known good backup with current files. Look for anomalies such as encrypted files or unusual file size changes in backup data. Use hash-based integrity checking tools (like Azure Backup's integrity checks) to identify corrupted or encrypted backups.
• Determine Backup History: Identify which backups were created before the attack to locate clean restore points. If your backup solution includes versioning, leverage that to identify and restore unencrypted versions.

3. Triage and Prioritization

• Prioritize Critical Systems: Focus on identifying and restoring the most critical systems first (e.g., domain controllers, databases, financial systems). Establish a priority list for recovery based on the business impact of the affected systems.
• Review Business-Critical Data: Identify the business-critical data that may have been compromised and ensure that the recovery of this data is prioritized.

4. Recovery Options

• Restore from Backups: After verifying the integrity of your backups, restore affected systems and data from clean backups. Ensure that the restored data is not re-encrypted by residual ransomware.
• Isolated Recovery Environment (IRE): Restore the data into an isolated recovery environment where you can verify that no malicious code is still present before reconnecting the systems to the network.
• Use Azure Backup with Immutable Storage: If you've used immutable storage for your backups (e.g., Azure Blob Storage with immutable policies), this storage ensures that your backups cannot be modified after creation, preventing ransomware from encrypting them. Restore from these immutable backups.
• Use Shadow Copies (if available): For Windows-based systems, check if Shadow Copies are available and use them to restore files to a previous state. However, ensure the ransomware hasn't also deleted these snapshots.
• Seek Ransomware Decryption Tools: If known ransomware is involved, search for free decryption tools from trusted sources (e.g., NoMoreRansom, security vendors). These tools may help recover encrypted data without paying the ransom.

5. Forensic Investigation and Analysis

• Engage Forensic Experts: If the attack is severe and the extent of the damage is unclear, consider engaging cybersecurity forensic experts to conduct an in-depth investigation. They can help identify the ransomware variant, infection vector, and impacted data.
• Analyze Logs and Alerts: Use tools like Azure Sentinel to review security logs, detect unusual activity, and correlate events related to the attack. This can help in understanding the full scope of the breach.

6. Mitigation and Remediation

• Patch Vulnerabilities: Identify and patch the vulnerabilities that allowed the ransomware to enter the system (e.g., unpatched software, open RDP ports, phishing emails). Use security tools like Microsoft Defender for Cloud to find and mitigate weaknesses.
• Clean Compromised Systems: After restoring systems from backups or clean images, scan the environment for any remnants of malware using endpoint protection solutions such as Microsoft Defender for Endpoint or third-party AV solutions.
• Rebuild Systems (if necessary): In cases of severe compromise, it may be safer to rebuild systems entirely from clean images rather than attempting to clean infected systems.

7. Review Backup Strategy

• Adopt a 3-2-1 Backup Rule: Ensure that you have three copies of your data stored in two different media formats, with at least one copy stored offsite (ideally in an isolated and immutable form). Regularly test your backups to ensure their integrity.
• Implement Immutable Backups: Use immutable backups (e.g., Azure Backup with immutable storage, Write-Once-Read-Many policies) to prevent tampering and ensure that even during a ransomware attack, your backups remain intact.

8. Post-Incident Recovery

• Monitor for Re-Infection: After recovery, closely monitor the network and systems for signs of re-infection. Pay attention to unusual network activity, file changes, and system performance.
• Update Incident Response Plan: Update your incident response plan based on lessons learned from the attack. Ensure that your team is prepared for future incidents with clear recovery steps.
• Improve Security Posture: Harden your security measures to prevent future attacks. Implement the latest security controls, monitor your environment using Azure Sentinel, and ensure all critical systems have the necessary protections in place.

9. Notify Stakeholders

• Communicate with Stakeholders: Depending on the severity of the ransomware attack, communicate with stakeholders, clients, regulators, and potentially law enforcement. Transparency about the incident and mitigation efforts is essential, especially if customer data was involved.

10. Consider Cyber Insurance and Legal Counsel

• Engage Cyber Insurance: If you have cyber insurance, notify your insurance provider as they may offer support for recovery efforts, including covering the costs of forensic investigations or legal assistance.
• Seek Legal Counsel: Depending on the severity of the attack and the jurisdiction, you may need to seek legal counsel, particularly if data breaches have occurred.

Summary

The key to effectively managing a ransomware attack is to act swiftly to contain the damage, assess the scope of the infection, and recover from clean backups. Restoring data should be done with caution, ensuring no residual ransomware remains to reinfect systems. Long-term, updating your security posture, backup strategy, and incident response plan are essential to preventing future attacks.