Full Report
Key Takeaways The DFIR Report Services → Click here to access the DFIR Lab related to this report ← Five new sigma rules were created from this report and added … Read More
Analysis Summary
# Incident Report: IcedID Loader Precedes ALPHV Ransomware Deployment via ScreenConnect and CSharp Streamer
## Executive Summary
In October 2023, an organization suffered a compromise initiated via a spam campaign distributing a forked IcedID loader. The threat actor rapidly escalated privileges using ScreenConnect and CSharp Streamer, culminating in a domain-wide deployment of ALPHV ransomware eight days after initial access. The attack showcased a multi-stage toolset leveraging legitimate remote access software for command execution and lateral movement.
## Incident Details
- **Discovery Date:** Not explicitly stated, but subsequent activity was observed starting in October 2023.
- **Incident Date:** Began in October 2023.
- **Affected Organization:** Not explicitly disclosed (Case Artifacts referenced).
- **Sector:** Not explicitly disclosed.
- **Geography:** Not explicitly disclosed.
## Timeline of Events
### Initial Access
- **Date/Time:** October 2023 (Start date).
- **Vector:** Malicious email/Spam Campaign delivering a forked IcedID loader.
- **Details:** The email contained a zip archive holding a Visual Basic Script (VBS) and a benign README file. User interaction executed the VBS, starting the IcedID loader, which established persistence via a scheduled task before downloading an IcedID DLL.
### Lateral Movement
- **Date/Time:** Approximately two minutes after execution (Discovery); ~2 hours after execution (ScreenConnect deployment).
- **Vector:** ScreenConnect (T1219) and Impacket’s wmiexec (used for remote ScreenConnect installation).
- **Details:** Initial reconnaissance used native binaries. The attacker installed ScreenConnect on the beachhead. After gaining domain controller access via `dcsync` and subsequent lateral movement, they copied a renamed ScreenConnect installer to a domain controller and executed it remotely using `wmiexec`.
### Data Exfiltration/Impact
- **Date/Time:** Day 8 post-intrusion.
- **Vector:** Custom staging and exfiltration tool utilizing Rclone.
- **Details:** Eight days after initial access, ALPHV ransomware was deployed across all domain-joined Windows systems. Data was staged and exfiltrated using a custom tool employing Rclone.
### Detection & Response
- **How it was discovered:** Not explicitly stated how the intrusion was definitively discovered, though related Cobalt Strike activity was being tracked by the reporting entity prior to the case being made public.
- **Response actions taken:** Containment, eradication, and recovery details are not fully enumerated in the provided text snippet, but the response focused on addressing the ransomware deployment and associated malware.
## Attack Methodology
- **Initial Access:** Phishing (T1566) via spam emails leading to **Forked IcedID Loader** execution via VBS.
- **Persistence:** Scheduled Task creation.
- **Privilege Escalation:** Achieved via **`dcsync` operation** from the beachhead host to a Domain Controller (T1003.006).
- **Defense Evasion:** Use of legitimate tools (ScreenConnect, Cobalt Strike) and obfuscated execution methods (PowerShell cradles, `bitsadmin`, `certutil`).
- **Credential Access:** Accessing **LSASS process** using CSharp Streamer (T1003.001).
- **Discovery:** Native Windows binaries (`nltest`, `net`), `systeminfo`.
- **Lateral Movement:** **ScreenConnect (T1219)** deployed via **wmiexec** on the Domain Controller.
- **Collection:** Data staging and exfiltration using a **custom tool with Rclone (T1560.001)**.
- **Exfiltration:** Data exfiltration using Rclone.
- **Impact:** **ALPHV Ransomware deployment (T1486)** across the domain.
## Impact Assessment
- **Financial:** Not explicitly estimated.
- **Data Breach:** Staged and exfiltrated data using Rclone (Type/volume not detailed).
- **Operational:** Full business lockout due to domain-wide ALPHV ransomware deployment.
- **Reputational:** Not explicitly stated.
## Indicators of Compromise
- **Network indicators:** Cobalt Strike Command and Control servers (Specific IPs defanged).
- **File indicators:** Forked IcedID loader, IcedID DLL, ScreenConnect installer (`toovey.exe`), Cobalt Strike beacons, `cslite.exe` (**CSharp Streamer**).
- **Behavioral indicators:** Scheduled Task creation, `nltest` and `net` execution, PowerShell cradles, `bitsadmin`/`certutil` for downloads, LSASS access, `dcsync` activity, Rclone execution.
## Response Actions
- **Containment:** (Implied: Halting WMI/SMB activity, potentially isolating infected hosts).
- **Eradication:** (Implied: Removing IcedID, Cobalt Strike, CSharp Streamer, and ScreenConnect instances).
- **Recovery:** (Implied: Restoring systems encrypted by ALPHV ransomware).
## Lessons Learned
- The convergence of loaders (IcedID) with post-exploitation tools (ScreenConnect, CSharp Streamer) allows for rapid domain compromise.
- The use of legitimate remote access tools like ScreenConnect can serve as a highly effective pivot for command and control on compromised hosts.
- Reliance on defensive tools to monitor known C2 frameworks (like Cobalt Strike) is crucial for early detection.
## Recommendations
- Enhance email filtering to prevent delivery of malicious archives containing VBS/script payloads.
- Implement strict endpoint controls to restrict the execution of remote access software (e.g., ScreenConnect) unless explicitly authorized via managed deployment systems.
- Deploy advanced detection logic for LSASS memory access, especially when initiated by non-standard processes like CSharp Streamer.
- Review and strengthen Domain Controller security against common privilege escalation methods, particularly monitoring for `dcsync` activity.