A sophisticated espionage campaign leveraging a previously unknown malware strain dubbed GONEPOSTAL, attributed to the notorious Russian state-sponsored group KTA007, better known as Fancy Bear or APT28.
The malware transforms Microsoft Outlook into a covert command and control channel, representing a significant evolution in living-off-the-land attack techniques.
Cybersecurity firm Kroll has uncovered a GONEPOSTAL operates through a carefully orchestrated two-stage attack mechanism designed to establish persistent backdoor access through email communications.
The malware consists of a malicious dropper DLL disguised as Microsoft’s legitimate SSPICLI.dll file, which handles security support provider interfaces for authentication tasks. This deceptive approach allows the malware to operate undetected while maintaining normal system functionality.
The attack begins when the malicious SSPICLI.dll forwards all 105 exported library functions to a renamed legitimate DLL (tmp7EC9.dll), ensuring applications continue to function normally.
However, the malicious code executes two critical C++ functions from the DLLMain execution path, initiating a PowerShell command sequence that establishes the foundation for the email-based backdoor.
The dropper’s PowerShell commands serve multiple purposes, including copying a file named “testtemp.ini” to the Outlook profile directory as “VbaProject.OTM” and implementing redundant victim identification mechanisms.
These mechanisms utilize DNS lookups and HTTP requests to external services like webhook.site and oast.fun, allowing attackers to obtain victim usernames and IP addresses for targeted email communication.
Registry Manipulation for Persistent Access
GONEPOSTAL employs sophisticated registry modifications to ensure persistent access and reduce detection likelihood.
The second method provides a useful backup should the HTTP request be blocked by an organization’s security tools such as reputation-based proxies.
The malware sets three critical Windows registry values that fundamentally alter Outlook’s security posture.
The “LoadMacroProviderOn” setting enables automatic loading of macro providers during Outlook startup, while the “Level” setting allows all macros to execute without restriction.
Perhaps most insidiously, the malware modifies the “PONT_STRING” registry key to suppress security warnings that would normally alert users to potentially malicious content downloads.
This registry manipulation effectively blinds users to the malware’s presence while ensuring seamless execution of malicious macros upon each Outlook startup.
The core functionality resides in the password-protected VbaProject.OTM file, which houses obfuscated VBA macros that transform Outlook into a fully functional backdoor.
While password protection provides an initial layer of obscurity, security researchers can bypass this protection using hex editors, though the scrambled strings and symbols complicate analysis.
However, since symbols and variable names are reused throughout the code, observing execution and surrounding logic allows for the macro file to be reconstructed to a format which is more easily parsed by humans.
The malware implements a comprehensive email monitoring and command processing system through several interconnected functions.
Upon Outlook startup, the Application_MAPILogonComplete() function triggers initialization processes that decode configuration strings, establish directories, and prepare command execution payloads.
The system then monitors incoming emails through Application_NewMailEx(), analyzing each message for command signatures.
GONEPOSTAL supports four primary command types: “cmd” for executing commands with output capture, “cmdNo” for silent command execution without output, “upload” for writing files to disk, and “download” for reading and chunking files for exfiltration.
The malware processes commands by decoding base64-encoded payloads with defined offsets, similar to configuration string encoding mechanisms.
Data Exfiltration Capabilities
The malware incorporates sophisticated file handling capabilities designed to facilitate data exfiltration through email attachments.
Files designated for exfiltration undergo base64 encoding before being split into approximately 3.15-megabyte chunks to accommodate email size limitations.
This chunking mechanism enables transfer of substantial data volumes while avoiding detection by standard email security systems.
The system maintains detailed dictionaries of processed emails, including generated email IDs, recipient addresses, subjects, and decoded command strings.
Error handling mechanisms ensure robust operation by logging failures and maintaining operational continuity even when individual commands encounter issues.
Following command execution, the malware creates and sends Outlook emails to predetermined attacker addresses, encoding response data in email bodies and attaching chunked files as necessary.
The system then performs cleanup operations by removing processed emails from both the inbox and deleted items folder, eliminating forensic evidence of the communication.
KTA007, operating under various aliases including Fancy Bear, APT28, and Pawn Storm, represents one of the most persistent state-sponsored threat actors associated with Russia’s Main Intelligence Directorate (GRU) Unit 26165.
The group maintains an extensive operational history encompassing high-profile attacks against the Democratic National Committee in 2016, the International Olympic Committee, and the Norwegian Parliament.
The group’s tactical arsenal spans zero-day exploitation, sophisticated spear-phishing campaigns, and deployment of both commercial and custom malware solutions.
GONEPOSTAL represents a significant evolution in their capabilities, demonstrating advanced understanding of enterprise email systems and innovative approaches to maintaining persistent access within targeted networks.
This campaign exemplifies the living-off-the-land methodology, leveraging legitimate business tools and communication channels for malicious purposes.
By utilizing Outlook’s native functionality, the malware achieves a level of stealth that traditional network-based command and control systems cannot match, as email communications appear legitimate to most security monitoring systems.
While Outlook-based persistence techniques have been observed from other advanced persistent threat groups, including KTA488 (APT32), GONEPOSTAL’s sophisticated implementation and comprehensive feature set distinguish it as a particularly concerning development.
Many organizations lack specific detection mechanisms for VbaProject.OTM file behavior or registry modifications that enable macro loading during Outlook startup.
The emergence of GONEPOSTAL underscores the critical need for enhanced email security monitoring, particularly regarding macro execution and registry modifications affecting Microsoft Office applications.
Organizations should implement robust detection mechanisms for unusual VbaProject.OTM file activity and establish comprehensive logging for registry changes affecting Office security settings.
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