Incident Response Guide: RansomHub Ransomware

Incident Triage Steps

Within the first 30 minutes, your priority is to confirm the incident, assess its scope, and determine if data theft occurred. RansomHub operators often engage in double-extortion, exfiltrating data before encryption.

1. Confirm the Incident: Look for RansomHub’s calling cards. These include:

   • Ransom notes named README.txt, RESTORE_FILES.txt, or HOW_TO_RECOVER_FILES.txt dropped in multiple directories.
   • A systematic change of file extensions to a new, consistent extension (e.g., .rhub, .rnum, or a random string). Encrypted files often have markers like [id-<VICTIM_ID>][email<ATTACKER_EMAIL>].rhub.
   • Check key system directories (C:\, C:\Users\Public, user desktops) for these notes.

2. Identify Patient Zero and Scope: Immediately query your EDR solution and SIEM platform.

   • Search for process creation events related to cmd.exe, powershell.exe, wscript.exe, or mshta.exe spawning vssadmin.exe or wbadmin.exe with arguments to delete shadow copies (e.g., vssadmin delete shadows /all /quiet). This is a core preparatory step for RansomHub.
   • Correlate these events with the creation of suspicious, randomly named executables in C:\Windows\Temp\, C:\Users\<user>\AppData\Local\Temp\, or C:\ProgramData\.
   • Identify the first host showing these behaviors. Examine its logs for recent remote access (RDP, VPN) or email-based activity (malicious attachments/links) which are common initial vectors.

3. Determine Data Exfiltration: Assume data was stolen. RansomHub actors typically use tools like rclone or MegaSync for exfiltration.

   • In your network security logs, look for large, sustained outbound data transfers (SMB, FTP, HTTPS) to unfamiliar cloud storage IP addresses or domains in the hours/days before encryption began.
   • On the suspected patient zero system, check for the presence of archiving tools (7zG.exe, WinRAR.exe) or cloud sync clients not part of your standard image, and review their execution logs.
   • Check Windows Event Logs (Event ID 4688) for command lines containing copy, robocopy, or rclone commands targeting large file shares or databases.

Evidence Collection

Before any containment or remediation actions, preserve the following evidence for forensic analysis and potential legal requirements.

• Memory Dumps: Use a trusted, pre-installed memory acquisition tool to capture the RAM of actively infected systems, especially those where encryption may still be running. This can reveal encryption keys, C2 addresses, and other malware components.
• Process List & Disk Artifacts: From a clean forensic workstation or using trusted CLI tools, collect:
  • A running process list with full command lines (e.g., tasklist /v or ps commands).
  • The ransom note and a sample of encrypted files.
  • Any suspicious executables found in temporary directories. RansomHub payloads are often named with random strings (e.g., fG43tq.exe, svcupdate.exe).
  • Prefetch files (C:\Windows\Prefetch\) and Shim Cache entries, which can show historical execution.
• Registry Artifacts: Collect relevant registry hives or specific keys. RansomHub may create persistence via Run keys:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run
  • HKLM\Software\Microsoft\Windows\CurrentVersion\Run
• Network Logs: Preserve full packet captures (PCAP) from border firewalls, internal network sensors, and from affected hosts if possible. Focus on traffic leading up to and during the encryption event. Flag any communication with known-bad IPs associated with RansomHub C2.

Containment Procedures

Goal: Isolate the threat while preserving evidence for eradication.

1. Network Segmentation:

   • Immediately quarantine infected segments at the network layer. Use firewall rules to block all inbound/outbound traffic from the VLANs or IP ranges containing affected systems.
   • If full segmentation is slow, isolate critical assets (domain controllers, backup servers, file servers) by blocking traffic from the compromised subnet.

2. Credential Reset Scope: RansomHub actors often leverage compromised credentials for lateral movement.

   • Reset passwords for all accounts that were active on the initially compromised host(s). This includes local admin accounts and any domain accounts used for service logons on that machine.
   • Immediately revoke Kerberos Ticket Granting Tickets (TGTs) for these accounts across the domain.
   • Consider a broader domain-wide password reset if lateral movement appears extensive.

3. C2 and Threat Actor Communication Blocking:

   • Update your perimeter and internal firewall, proxy, and DNS filtering solutions to block all communication to the C2 servers and exfiltration endpoints listed in the ransom note.
   • Block the email addresses and Tox IDs provided in the ransom note at your email gateway to prevent operator communication.
   • Be aware that RansomHub may use dynamic DNS or fast-flux domains; implement rules to block newly-registered domains (NRDs) and domains with a low reputation score.

Eradication and Recovery

This phase involves complete removal and restoration of operations.

1. Complete Removal: Follow the detailed, step-by-step instructions in the RansomHub Removal Guide for each affected endpoint. This guide provides specific commands and procedures to:

   • Terminate malicious processes.
   • Remove RansomHub files, registry entries, and scheduled tasks.
   • Eliminate any persistence mechanisms.

2. Restoring from Backups: Do not pay the ransom. Use your offline, immutable backups for recovery.

   • Before restoration, ensure the backup media and the restoration management system are fully isolated from the network and verified as clean.
   • Rebuild infected systems from a known-clean base image (gold image) rather than restoring over a compromised OS.
   • Restore encrypted data from backups to the clean systems. Validate file integrity after restoration.

3. Verifying a Clean State: Before returning systems to production:

   • Perform a full anti-malware scan with updated signatures across all restored systems.
   • Use a dedicated endpoint detection and response query or host-based inspection tool to hunt for any remaining IOCs (Indicators of Compromise) related to RansomHub, such as specific mutexes or file hashes.
   • Monitor the reintroduced systems closely for any anomalous network or process activity for a defined period.

Lessons Learned Checklist

After containment and recovery, conduct a formal post-incident review. Answer these questions specific to RansomHub’s attack chain:

• Initial Access: How did RansomHub gain entry? Was it via a phishing email with a malicious macro, exploitation of a public-facing application (like a VPN vulnerability), or compromised remote desktop credentials? Review email gateway logs, firewall connection attempts, and failed RDP logins.
• Control Failures: Which security controls did not perform as intended?
  • Was endpoint protection not configured to block execution from user temp directories?
  • Did application allowlisting fail to prevent unauthorized tools like rclone or vssadmin from running?
  • Were network segmentation controls insufficient to prevent lateral movement from a user workstation to critical servers?
• Detection Gaps: Why wasn’t the activity detected earlier? Review your SIEM alerts and EDR console.
  • Were there no alerts for vssadmin.exe delete shadows commands? (A key RansomHub precursor).
  • Were large data transfers to unfamiliar cloud IPs not flagged by your data loss prevention or network monitoring tools?
  • Did your intrusion detection system have updated signatures for RansomHub’s network traffic patterns?
• Improvement Plan: Based on the answers above, define actionable improvements:
  • Technical: Implement stricter email attachment filtering, enforce multi-factor authentication on all remote access, ensure immutable/offline backups are tested, and deploy canary tokens on critical file shares.
  • Process: Update your incident response playbook with RansomHub-specific triage steps. Conduct tabletop exercises simulating a double-extortion ransomware attack.
  • Awareness: Reinforce user training on identifying sophisticated phishing attempts, especially those delivering payloads that lead to ransomware.

For proactive measures, refer to the RansomHub Detection Guide. For more background on this threat, see the RansomHub Overview.