APT28's Operation MacroMaze: Unmasking Webhook-Driven Macro Malware Against European Entities

APT28's Operation MacroMaze: Unmasking Webhook-Driven Macro Malware Against European Entities

The cybersecurity landscape continues to evolve with nation-state threat actors demonstrating increasing sophistication and adaptability in their tactics, techniques, and procedures (TTPs). Among these, the Russia-linked advanced persistent threat (APT) group known as APT28, also tracked as Fancy Bear, Strontium, or Pawn Storm, has once again emerged as a significant threat. A new campaign, codenamed Operation MacroMaze by S2 Grupo's LAB52 threat intelligence team, has been attributed to APT28, specifically targeting strategic entities across Western and Central Europe. Active between September 2025 and January 2026, this operation underscores a persistent reliance on fundamental yet effective tooling, notably leveraging webhook-based macro malware and exploiting legitimate online services for command and control (C2) and data exfiltration.

APT28: A Persistent and Evolving Threat Actor

APT28 has a long and notorious history of cyber espionage, typically focusing on governmental, defense, energy, and media organizations globally, with a particular emphasis on NATO member states and countries of geopolitical interest to Russia. Known for its extensive use of spear-phishing, zero-day exploits (though less so in this campaign), and sophisticated malware frameworks, APT28 consistently adapts its methodologies to bypass contemporary security controls. Operation MacroMaze highlights a return to foundational attack vectors, proving that even "basic tooling" can be highly effective when executed with precision and persistence against specific, high-value targets.

Operation MacroMaze: Unveiling the Campaign Architecture

The campaign's operational period from September 2025 to January 2026 saw a concentrated effort against a spectrum of European organizations. The initial access vector for Operation MacroMaze predominantly involved highly crafted spear-phishing emails. These emails delivered weaponized Microsoft Office documents, primarily Word or Excel files, embedded with malicious macros. Upon execution, these macros initiated the subsequent stages of the attack chain.

A distinctive feature of Operation MacroMaze is its reliance on webhook-based communication. Instead of establishing direct, easily detectable C2 channels, the malicious macros were engineered to leverage webhooks hosted on legitimate online services. This technique offers several advantages to the threat actor:

• Evasion: Traffic to legitimate services (e.g., Discord, Slack, Microsoft Teams, Trello) often bypasses traditional network intrusion detection systems (NIDS) and firewalls due to its benign nature.
• Stealth: Webhooks provide an asynchronous, low-profile method for initial beaconing, C2 instructions, and small-scale data exfiltration, blending seamlessly with normal organizational network traffic.
• Availability: These services are robust and widely available, offering a resilient infrastructure for threat actors without needing to maintain their own C2 servers.

The primary function of these macros, once executed, was to collect initial system reconnaissance data (e.g., hostname, user information, operating system details, installed security products) and exfiltrate it via the configured webhook URL. This initial reconnaissance phase is critical for APT28 to assess the target environment and determine subsequent, more targeted payload delivery or lateral movement.

Technical Deep Dive: Macro Malware Analysis

Analysis of the macro malware employed in Operation MacroMaze reveals several key characteristics:

• Obfuscation Techniques: The VBA (Visual Basic for Applications) code within the documents was often heavily obfuscated using various methods, including string concatenation, character manipulation, base64 encoding, and junk code insertion. This complicates static analysis and evades signature-based detection.
• Environment Checks: Some samples included logic to detect virtualized environments or sandboxes, preventing execution or altering behavior if a forensics tool was identified. This is a common anti-analysis technique.
• Payload Delivery: While the initial macro's primary role was reconnaissance and webhook communication, it often served as a downloader for subsequent stages. This could involve fetching additional payloads (e.g., PowerShell scripts, .NET assemblies, custom droppers) from remote servers or directly via the webhook's response mechanism, further extending the attack's capabilities.
• Persistence Mechanisms: Although the campaign relied on basic tooling, persistence was likely achieved through standard methods such as modifying registry run keys, creating scheduled tasks, or exploiting legitimate software functionalities to ensure continued access to compromised systems.

Leveraging Legitimate Services for C2 and Exfiltration

The choice of legitimate services like Discord webhooks is a strategic one for APT28. These platforms offer readily available APIs that can be abused for covert communication. A typical scenario involves the macro sending an HTTP POST request to a specific webhook URL, containing exfiltrated data in the request body. The webhook then relays this information to a Discord channel or similar platform controlled by APT28. This method allows for:

• Minimal infrastructure overhead for the attacker.
• High likelihood of successful egress communication through enterprise firewalls.
• Challenges in distinguishing malicious traffic from legitimate user activity.

The data exfiltrated in the initial phase typically includes system metadata, network configuration, and potentially user credentials or sensitive documents if the macro had elevated privileges or exploited vulnerabilities to gain them.

Defensive Strategies and Threat Hunting

Defending against campaigns like Operation MacroMaze requires a multi-layered approach:

• Endpoint Security Enhancements:
  • Macro Disabling: Implement strict policies to disable macros by default, especially for documents originating from the internet. Educate users on the risks and train them to never enable content unless absolutely verified.
  • Attack Surface Reduction (ASR) Rules: Configure ASR rules to block all Office applications from creating child processes or injecting code into other processes.
  • Behavioral Analysis: Deploy Endpoint Detection and Response (EDR) solutions capable of detecting anomalous process behavior, such as Office applications initiating outbound network connections to unusual destinations or executing suspicious PowerShell commands.
• Network Security Controls:
  • Egress Filtering: Implement robust egress filtering to restrict outbound connections to only necessary ports and protocols. While difficult for legitimate services, monitoring for unusual volumes or patterns of webhook traffic to known legitimate services can be indicative.
  • Proxy and Firewall Log Analysis: Regularly analyze proxy and firewall logs for connections to legitimate services that appear suspicious in context (e.g., connections from server-side systems, unusual user-agents, high frequency from single hosts).
  • DNS Monitoring: Monitor for suspicious DNS queries that might precede C2 establishment or data staging.
• User Awareness Training: Continuous and effective security awareness training is paramount to educate users about spear-phishing tactics, the dangers of enabling macros, and reporting suspicious emails.

Digital Forensics and Incident Response

Responding to an intrusion like Operation MacroMaze necessitates a thorough digital forensic investigation:

• Log Analysis: Meticulous examination of Windows Event Logs (e.g., Security, System, PowerShell operational logs), firewall logs, proxy logs, and EDR telemetry to trace the initial infection vector, execution chain, and C2 communications.
• Malware Analysis: Static and dynamic analysis of the weaponized documents and any downloaded payloads to understand their full capabilities, C2 infrastructure, and indicators of compromise (IOCs). This includes de-obfuscating VBA code and analyzing network traffic generated by the malware.
• Link Analysis & Attribution: During incident response, particularly when tracing initial access vectors or suspicious C2 communication paths, tools for advanced telemetry collection are invaluable. Services like grabify.org, while often associated with less sophisticated social engineering, can be adapted by forensic analysts to meticulously collect critical metadata such as IP addresses, User-Agent strings, Internet Service Provider (ISP) details, and detailed device fingerprints from suspicious links. This granular data aids significantly in profiling initial reconnaissance attempts, pinpointing geographic origins, and enriching threat intelligence for subsequent attribution efforts, even when dealing with sophisticated threat actors who may inadvertently trigger such logging mechanisms through their initial probing or C2 testing.
• Threat Intelligence Integration: Leverage threat intelligence feeds and collaborate with intelligence partners to identify known IOCs associated with APT28 and Operation MacroMaze.

Conclusion

Operation MacroMaze serves as a stark reminder that even well-known and extensively tracked APT groups like APT28 continue to refine their methodologies, often by reverting to and enhancing "basic" attack vectors. The exploitation of legitimate services through webhook-based macro malware presents a significant challenge for traditional security defenses. Proactive threat intelligence, robust endpoint and network security controls, continuous user education, and a well-rehearsed incident response plan are indispensable for mitigating the risks posed by such persistent and adaptive state-sponsored threats targeting critical European infrastructure.