Trojan.W97M.EMOTET.SMI: Analyzing the Persistent Emotet Threat Targeting Windows Systems

Trojan.W97M.EMOTET.SMI is a variant of the notorious Emotet malware, primarily spread through malicious Microsoft Office documents. Despite its “Low” overall risk rating, it poses a Medium damage potential, making it a concern for organizations relying on Windows-based systems. This Trojan typically infiltrates systems via malicious email attachments or compromised websites, often acting as a downloader for additional payloads.

Key Takeaways

Threat Type: Trojan (Downloader)
Aliases: HEUR:Trojan.Script.Generic (Kaspersky), TrojanDownloader:O97M/Emotet.S!MTB (Microsoft)
Platforms: Windows
Primary Infection Vectors: Malicious Office documents, drive-by downloads
Current Risk: Low reported infections but moderate damage potential
Associated Threat Actors: Historically linked to Mealybug (Emotet’s operators) and recent campaigns involving ShadowSyndicate affiliates.

Technical Analysis

Infection Mechanism

Trojan.W97M.EMOTET.SMI is typically delivered through malicious Office documents (Word or Excel files with embedded macros) or dropper malware distributed by other families like IcedID. Once executed, it drops additional payloads (e.g., Cobalt Strike or ransomware), establishes persistence via registry modifications, and communicates with hardcoded C2 servers.

Detection Evasion Techniques

This variant employs macro obfuscation with junk VBA code to bypass static analysis and leverages living-off-the-land tactics (e.g., PowerShell) for lateral movement. Recent campaigns have shown connections to IPs like 46.161.27.151, linked to ShadowSyndicate operations.

Relevance to Security Teams

For Blue Teams & SOC Analysts

Indicators of Compromise (IoCs):

Type	Value	Description
IP	`46.161.27.151`	C2 server linked to ShadowSyndicate
Filename	`README_[a-zA-Z0-9]{6}.txt`	RansomHub ransom note pattern
HTTP User-Agent	`rclone`	Data exfiltration to MEGA

Detection Rule (Sigma):

title: Emotet Macro Detection  
description: Detects obfuscated VBA macros in Office files  
rule:  
  strings:  
    $s1 = "AutoOpen" nocase  
    $s2 = "WScript.Shell" nocase  
  condition:  
    all of them

For Red Teams

Simulate Emotet behavior using Covenant C2 with macro-enabled Word docs. Test detection against models like Antigena SMB Enumeration Block to evaluate defensive coverage.

Remediation & Mitigation

Disable Office Macros: Enforce Group Policy to block macros from untrusted sources.
Network Segmentation: Limit SMB/RDP access to critical systems.
Endpoint Protection: Deploy behavior-based solutions like Darktrace’s Autonomous Response.

“Emotet’s resurgence highlights the need for anomaly-based detection to combat evolving C2 tactics.” — Darktrace Threat Research Team

Conclusion

While Trojan.W97M.EMOTET.SMI currently has low distribution rates, its role in delivering high-impact payloads like RansomHub warrants vigilance. Organizations should prioritize macro security and monitor for anomalous SSH/SMB traffic to mitigate risks.