APT28’s Operation MacroMaze: Webhook Macros and Browser-Based Exfiltration in Europe
- Javier Conejo del Cerro
- hace 10 horas
- 3 Min. de lectura
Between September 2025 and January 2026, the Russia-linked state-sponsored threat actor APT28 conducted Operation MacroMaze, targeting selected government, diplomatic, defense-adjacent, and strategic entities across Western and Central Europe.
Rather than relying on zero-days or complex exploit chains, the campaign demonstrates how carefully orchestrated use of macros, batch scripts, and legitimate webhook services can achieve stealthy persistence and browser-based data exfiltration — proving that operational discipline can outweigh technical novelty.
Phase 1: Initial Access – Spear Phishing as a Controlled Beacon
The campaign begins with spear-phishing emails delivering Microsoft Office documents.
A distinctive structural element is embedded within the document’s XML:
INCLUDEPICTURE
This field points to a webhook[.]site URL hosting a JPG image.
When the document is opened, the image is fetched automatically, triggering an outbound HTTP request. This functions as a tracking pixel-style beacon, allowing the operator to confirm:
The document was opened
The recipient’s IP and metadata
Timing of interaction
This early validation layer reduces operational noise and confirms viable targets before deploying further payloads.
Phase 2: Macro Execution and Loader Chain
Once the victim enables macros, the infection chain progresses through multiple stages:
Macro execution
Launch of a Visual Basic Script (VBS)
Execution of a CMD file
Launch of a batch script
Persistence is established through scheduled tasks, ensuring execution survives reboots.
The campaign evolved over time:
Early variants relied on Microsoft Edge headless execution
Later versions used SendKeys keyboard simulation to bypass security prompts
Some variants aggressively terminated other Edge processes to maintain execution control
Others moved browser windows off-screen to reduce user visibility
The tooling remains simple — but deliberately arranged for stealth.
Phase 3: Browser-Based Command Execution
The batch script renders a small Base64-encoded HTML payload inside Microsoft Edge.
Instead of deploying traditional exfiltration malware, APT28:
Loads HTML in hidden or off-screen Edge sessions
Retrieves a remote command from webhook[.]site
Executes the command locally
Captures the output
Submits results via HTML form submission back to a webhook endpoint
This approach leverages:
Standard browser functionality
Legitimate web services
Minimal disk artifacts
Exfiltration occurs through normal HTTP requests, blending with legitimate traffic.
The stolen or compromised data includes:
Command execution output
System information gathered via executed commands
Potential reconnaissance data from compromised hosts
The technique avoids traditional C2 binaries and reduces detection surfaces.
Phase 4: Infrastructure and Stealth Model
Operation MacroMaze demonstrates several key operational characteristics:
Abuse of legitimate webhook services for payload staging and exfiltration
Browser-based data transfer rather than custom C2 channels
Minimal custom malware footprint
Persistence via scheduled tasks
Evolution of evasion techniques over time
This is not a high-noise smash-and-grab campaign.
It is structured, quiet, and purpose-driven espionage.
Victim Profile
Targets were selected entities in Western and Central Europe, including:
Government institutions
Diplomatic bodies
Defense-related organizations
Strategic and policy-focused entities
This targeting aligns with APT28’s long-established intelligence collection objectives linked to Russian geopolitical interests.
Measures to Fend Off Operation MacroMaze
To mitigate similar macro-webhook campaigns:
Disable Microsoft Office macros by default
Block or monitor outbound traffic to webhook services
Inspect Office documents for suspicious XML elements (e.g., INCLUDEPICTURE external references)
Detect abnormal scheduled task creation
Monitor Microsoft Edge headless or hidden/off-screen execution
Inspect outbound HTML form-based data submissions
Deploy behavioral EDR to identify macro → VBS → CMD → batch execution chains
Restrict PowerShell and script interpreter execution where unnecessary
Apply email sandboxing to analyze macro-enabled attachments
Enforce least privilege on endpoints
Behavioral detection is critical — signature-based detection alone may miss this campaign.
Operation MacroMaze reinforces a recurring lesson in cyber espionage:
Simplicity, when carefully orchestrated, can be highly effective.
APT28 did not deploy sophisticated zero-days or complex rootkits. Instead, it:
Leveraged trusted browser functionality
Outsourced infrastructure to legitimate webhook platforms
Minimized disk artifacts
Evolved evasion techniques incrementally
Focused on stealth and persistence
This campaign reflects disciplined tradecraft rather than technical spectacle.
In an era dominated by discussions of AI-driven malware and advanced implants, MacroMaze is a reminder that well-structured macro abuse combined with browser-based exfiltration can remain highly effective against insufficiently hardened environments.
Stealth does not require complexity.
It requires precision.
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