Full Report
Disclosure: This article was provided by ANY.RUN. The information and analysis presented are based on their research and findings.
Analysis Summary
# Tool/Technique: Remcos RAT
## Overview
Remcos RAT (Remote Access Trojan) is deployed at the final stage of a stealthy phishing campaign, following execution via DBatLoader and obfuscated scripts. It is injected into legitimate system processes to carry out post-exploitation activities.
## Technical Details
- Type: Malware family (Remote Access Trojan)
- Platform: Windows
- Capabilities: Establishing remote access, executing commands, establishing persistence (via scheduled tasks), registry modification, file system manipulation.
- First Seen: Not explicitly mentioned in the text, but Remcos is a known RAT.
## MITRE ATT&CK Mapping
*Based on observed behaviors mentioned in the text:*
- T1059 - Command and Scripting Interpreter
- T1059.003 - Windows Command Shell (via cmd.exe execution)
- T1105 - Ingress Tool Transfer (Implied, as payloads are downloaded/executed)
- T1547 - Boot or Logon Autostart Execution
- T1547.001 - Registry Run Keys / Startup Folder (Persistence via Scheduled Tasks implies this goal)
- T1055 - Process Injection
## Functionality
### Core Capabilities
- Delivered as a final payload via an infection chain starting from a phishing email archive.
- Injected directly into legitimate system executables (`.exe` files).
- Executes commands via spawned `cmd.exe` processes.
- Establishes persistence through the creation of scheduled tasks.
### Advanced Features
- Stealthy execution achieved by abusing built-in Windows tools (LOLBAS abuse).
- Utilizes path manipulation tricks (e.g., using a mock directory like "C:\Windows " with a trailing space) to bypass User Account Control (UAC).
## Indicators of Compromise
- File Hashes: [Not provided in text]
- File Names: `Faktura.exe` (Lure file), `alpha.pif` (Dropper utilizing LOLBAS abuse), `Cmwdnsyn.url` (Used in scheduled task persistence).
- Registry Keys: Changes related to scheduled task creation are observed.
- Network Indicators: [Not provided in text, although implied C2 communication exists for a RAT]
- Behavioral Indicators: Injection into legitimate system processes; execution of obfuscated CMD scripts; creation of scheduled tasks; abuse of `esentutl.exe`.
## Associated Threat Actors
- Not explicitly named, but associated with a stealthy phishing campaign leveraged by DBatLoader.
## Detection Methods
- Signature-based detection: Ineffective against the fileless nature and custom obfuscation used.
- Behavioral detection: Critical for spotting the sequence: archive execution -> DBatLoader -> obfuscated scripts -> process injection -> persistence creation (scheduled tasks).
- YARA rules: Triggered by DBatLoader execution.
## Mitigation Strategies
- Deploying advanced sandbox analysis solutions (like ANY.RUN) to trace infection chains visually.
- Monitoring for unusual process trees originating from user interaction (e.g., archive opening).
- Implementing strict controls over LOLBAS usage, specifically monitoring `esentutl.exe` for unexpected file copy operations or renaming activities.
- Monitoring for scheduled task creation that points to anomalous file extensions (like `.url` or `.pif`).
- Hardening or auditing Windows mechanisms susceptible to UAC bypasses (like path string handling nuances).
## Related Tools/Techniques
- **Loader Malware:** DBatLoader
- **Delivery Lure:** `Faktura.exe` (posed as an invoice)
- **Scripting Obfuscation:** BatCloak-wrapped CMD files
- **Techniques:** LOLBAS Abuse (`esentutl.exe`), UAC Bypass (mock directory path handling).
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# Tool/Technique: DBatLoader
## Overview
DBatLoader is the initial loader malware executed after a victim opens a malicious archive resulting from the phishing email. Its primary role is to execute obfuscated command scripts that ultimately lead to the deployment of the Remcos RAT.
## Technical Details
- Type: Loader Malware
- Platform: Windows
- Capabilities: Initiating the infection chain, launching obfuscated scripts, serving as a trigger point for YARA detections.
- First Seen: Not explicitly mentioned.
## MITRE ATT&CK Mapping
- T1204 - User Execution
- T1204.002 - Malicious File
- T1059 - Command and Scripting Interpreter
- T1059.003 - Windows Command Shell (via spawning cmd.exe)
## Functionality
### Core Capabilities
- Executed upon archive opening.
- Spawns `cmd.exe` to begin the subsequent malicious script execution phase.
### Advanced Features
- Its presence triggers specific YARA rules, suggesting identifiable characteristics or imports prior to full payload delivery.
## Indicators of Compromise
- File Hashes: [Not provided in text]
- File Names: Executed from the initial malicious archive content.
- Registry Keys: [Not provided in text]
- Network Indicators: [Not provided in text]
- Behavioral Indicators: Appears in the process tree immediately after archive trigger, subsequently spawning `cmd.exe`.
## Associated Threat Actors
- Associated with threat actors utilizing the Remcos RAT via this specific phishing vector.
## Detection Methods
- **YARA rules:** Specifically mentioned as being triggered by DBatLoader.
- Behavioral Detection: Monitoring for immediate spawning of suspicious command shells (`cmd.exe`) after initial file execution.
## Mitigation Strategies
- Email gateway filtering to block malicious archives.
- Endpoint detection systems configured to detect suspicious process lineage (e.g., archive process spawning loaders).
## Related Tools/Techniques
- **Payload:** Remcos RAT
- **Technique:** Obfuscated CMD script execution.
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# Technique: Obfuscated CMD Scripts (BatCloak-Wrapped)
## Overview
`.cmd` scripts are obfuscated, often using techniques like BatCloak, to hide their malicious intent from static analysis tools. These scripts are used to download and execute the final malicious payload (Remcos RAT).
## Technical Details
- Type: Technique (Obfuscation/Execution)
- Platform: Windows (CMD)
- Capabilities: Hiding true execution commands, achieving persistence preparation, initiating payload delivery.
- First Seen: Not applicable (Technique).
## MITRE ATT&CK Mapping
- T1027 - Obfuscated Files or Information
- T1027.002 - Binary encoding (Implied mechanism for hiding CMD intent)
- T1059 - Command and Scripting Interpreter
- T1059.003 - Windows Command Shell
## Functionality
### Core Capabilities
- Conceal malicious command lines using obfuscation.
- Execute subsequent high-risk actions, including downloading and dropping the Remcos payload.
### Advanced Features
- Decoding instructions are revealed only during dynamic execution (as seen in sandbox command-line views).
## Indicators of Compromise
- File Hashes: [Not provided in text for the scripts themselves]
- File Names: `.cmd` files.
- Registry Keys: [Not provided in text]
- Network Indicators: Implied connections required for payload download.
- Behavioral Indicators: Suspicious string patterns when command lines are decoded; high entropy/unusual characters in script content before execution.
## Associated Threat Actors
- Unknown specific actors, but leveraging common obfuscation tactics.
## Detection Methods
- **Dynamic Analysis/Sandboxing:** Crucial for viewing decoded instructions.
- **Static Analysis:** Requires advanced emulation or pattern matching geared toward common obfuscators.
## Mitigation Strategies
- Script execution whitelisting/monitoring (AppLocker/WDAC).
- Utilizing process monitoring to detect command-line arguments associated with known obfuscation patterns.
## Related Tools/Techniques
- **Tool:** BatCloak (The specific obfuscator used).
- **Payload:** Remcos RAT.