Full Report
Key Takeaways Case Summary This intrusion began in November 2024 with a password spray attack targeting an internet-facing RDP server. Over the course of several hours, the threat actor attempted … Read More
Analysis Summary
# Incident Report: RDP Password Spray Leading to RansomHub Domain Compromise
## Executive Summary
This incident, initially detected in February 2025 but occurring in November 2024, began with a successful password spray attack against an exposed RDP server, leading to initial compromise. The threat actor rapidly escalated privileges, used discovery tools, exfiltrated data via Rclone, and ultimately deployed the RansomHub ransomware network-wide using remote service execution on lateral movement targets, including domain controllers.
## Incident Details
- **Discovery Date:** February 2025 (Original Threat Brief Publication)
- **Incident Date:** November 2024 (Intrusion Start)
- **Affected Organization:** Undisclosed specific customer
- **Sector:** Undisclosed (Implied Corporate/Enterprise)
- **Geography:** Undisclosed
## Timeline of Events
### Initial Access
- **Date/Time:** November 2024 (Start)
- **Vector:** External Remote Services (RDP Password Spray)
- **Details:** Threat actor targeted an internet-facing RDP server, attempting logins against numerous accounts over a four-hour period from known malicious IPs (based on OSINT).
### Lateral Movement
- **Date/Time:** Approximately two hours after initial authentication.
- **Details:** After gaining initial foothold, the actor used RDP to move laterally to two Domain Controllers (DCs). They used discovery commands (`net` commands, Advanced IP Scanner, NetScan) to map the internal network.
### Data Exfiltration/Impact
- **Data Exfiltration:** Data was exfiltrated using Rclone over an SFTP channel to a remote server.
- **Impact:** RansomHub ransomware was deployed network-wide, spreading via SMB and executed using remote services (implying potential domain-wide impact leveraging compromised highly privileged accounts).
### Detection & Response
- **Detection:** Specific detection artifacts noted include Mimikatz use, LSASS memory access, Rclone execution, and RansomHub deployment.
- **Response Actions:** Not explicitly detailed in the provided text beyond forensic capture (implied by the mention of the DFIR lab). Containment and eradication would have involved network segmentation, password resets, and ransomware removal.
## Attack Methodology
- **Initial Access:** Password Spraying (T1110.003) against RDP (T1021.001).
- **Persistence:** Not explicitly detailed, but likely utilizing valid accounts (T1078).
- **Privilege Escalation:** LSASS Memory Access (T1003.001) using Mimikatz to harvest credentials.
- **Defense Evasion:** Event log clearing (T1070.001) and use of living-off-the-land binaries (LOLBins).
- **Credential Access:** Mimikatz and Nirsoft CredentialsFileView execution to extract credentials from memory and files.
- **Discovery:** Used `net` commands, Advanced IP Scanner, and NetScan for network and system discovery (T1046, T1018, T1083).
- **Lateral Movement:** Used RDP (T1021.001), suggesting the use of valid credentials obtained during credential access.
- **Collection:** Focused on gathering credentials and sensitive data.
- **Exfiltration:** Rclone used to exfiltrate data via SFTP (Exfiltration Over Alternative Protocol - T1048).
- **Impact:** Data Encryption for Impact (T1486) via RansomHub ransomware deployment.
## Impact Assessment
- **Financial:** Not disclosed, but likely significant due to domain-wide ransomware deployment and required recovery efforts.
- **Data Breach:** Data was exfiltrated using Rclone over SFTP, type/volume unknown.
- **Operational:** Severe operational disruption due to network-wide RansomHub encryption.
- **Reputational:** Not detailed.
## Indicators of Compromise
- **Network indicators:** SFTP traffic utilized by Rclone.
- **File indicators:** Rclone binaries, Mimikatz artifact, RansomHub ransomware payload.
- **Behavioral indicators:** LSASS memory access from a non-system account, extensive use of `Net.EXE` for system discovery, Windows Event Log clearing using `wevtutil`.
## Response Actions
- **Containment:** (Inferred, based on post-compromise evidence) Isolating infected hosts, potentially disconnecting the network segment where lateral movement occurred.
- **Eradication:** (Inferred) Removing RansomHub binaries, auditing and resetting compromised credentials, and disabling the exposed RDP server.
- **Recovery:** (Inferred) Restoring systems from backups, re-imaging infected hosts, and rebuilding Domain Controllers if compromised credentials led to DCSync or similar domain takeover activities (note: DCSync T1003.006 is listed in accompanying TTPs).
## Lessons Learned
- RDP exposure remains a critical vulnerability, highly susceptible to brute-forcing aids like password spraying.
- Credential harvesting tools (Mimikatz) are highly effective when executed successfully post-initial access.
- Data exfiltration using legitimate tools like Rclone can evade simple network monitoring controls.
- Network-wide ransomware deployment indicates high-level domain compromise was achieved.
## Recommendations
- Implement Multi-Factor Authentication (MFA) on all remote access services, especially RDP.
- Restrict RDP access solely to known, trusted IP ranges via firewall policies.
- Enhance monitoring for post-exploitation tools like Mimikatz and unusual LSASS memory access patterns.
- Audit and reduce the use of living-off-the-land binaries for discovery tasks by standard users.
- Implement network segmentation to prevent ransomware from easily traversing the entire environment upon execution.