Full Report
Authored by By Yashvi Shah McAfee Labs have identified an increase in Wextract.exe samples, that drop a malware payload at... The post Deconstructing Amadey’s Latest Multi-Stage Attack and Malware Distribution appeared first on McAfee Blog.
Analysis Summary
# Threat Actor: Unspecified Actor Utilizing Wextract.exe as Delivery Mechanism
## Attribution & Identity
The specific threat actor is not named or attributed in the provided context. The analysis focuses on the *techniques* observed in malicious `wextract.exe` samples.
## Activity Summary
McAfee Labs observed an increase in malicious `wextract.exe` samples being used as a multi-stage delivery mechanism for various malware payloads, including **Amadey** and **Redline Stealer**. The primary activity involves exploiting the legitimate Windows utility `wextract.exe` (used for extracting CAB files) to introduce secondary malicious executables onto a victim's system.
## Tactics, Techniques & Procedures
- **Masquerading/Abuse of Legitimate Tools:** Using a fake or modified version of the legitimate Windows executable `wextract.exe` (located in System32) for malware distribution.
- **Payload Staging within PE Resources:** Storing additional executables (`cydn.exe` and `vona.exe`) within the resource section of the malicious PE file, specifically embedded within a specially crafted CABINET resource (accounting for 75.75% of the file size).
- **Chained Execution via PE Resources:** Utilizing undocumented or abused resource attributes (`RUNPROGRAM` and `POSTRUNPROGRAM`) within the PE file to dictate the order of execution for the staged payloads (`cydn.exe` executes first, followed by `vona.exe`).
- **Dropping Payloads:** Executing the staged files (`cydn.exe` and `vona.exe`) into the writable and often less secured `%TEMP%` directory.
- **Evasion:** Using techniques within the PE file structure (Russian language strings, copyright claims for Microsoft Corporation) to evade security software detection.
- **Data Exfiltration:** Establishing communication with Command and Control (C2) servers post-execution for data exfiltration.
- **Potential Objectives:** Information stealing (credentials, financial data), Remote Access (backdoors), and Ransomware delivery (though not explicitly confirmed for this chain, it is listed as a potential use case for modified `wextract.exe`).
- **MITRE ATT&CK IDs:** Not explicitly provided in the text.
## Targeting
- **Sectors:** Implied to target environments vulnerable to information stealing and potential endpoint compromise.
- **Geography:** Static strings observed in the samples contained Russian language, suggesting a possible link to Russian-affiliated actors or targeting infrastructure, but this is not a definitive attribution.
- **Victims:** Not specified beyond the general targets of Amadey and Redline Stealer operations (information theft).
## Tools & Infrastructure
- **Malware families used:** Amadey, Redline Stealer.
- **Staged Payloads:** `cydn.exe`, `vona.exe`.
- **Infrastructure:** Commander and Control (C2) servers utilized for data exfiltration (details not provided).
## Implications
This technique highlights a sophisticated use of legitimate Windows file structures (PE resources) for multi-stage malware delivery and execution, making detection significantly harder as the initial artifact appears to leverage Microsoft signing conventions and embedded data structures. Successful execution leads to the deployment of high-impact malware like credential stealers.
## Mitigations
- Implement strong application control/whitelisting to restrict execution from unusual locations like the `%TEMP%` folder.
- Enhance monitoring/detection of anomalous behavior within the PE resource section, specifically looking for large embedded CABINET resources or the use of `RUNPROGRAM`/`POSTRUNPROGRAM` indicators.
- Configure systems to distrust files masquerading as legitimate utilities like `wextract.exe` if they originate outside trusted installer paths.
- Analyze outbound network traffic for connection establishment to C2 infrastructure following file execution in temporary or user directories.