Office Test
Office Test [T1137.002]
Information
Introduction
The MITRE ATT&CK sub-technique "Office Test" (T1137.002) falls under the broader category of "Office Application Startup." This sub-technique specifically involves adversaries exploiting Microsoft Office's built-in testing mechanisms to execute malicious payloads. Attackers leverage Office Test registry keys, which are typically intended for debugging or testing purposes, to automatically launch malicious code whenever Office applications start. This method enables persistence and stealthy execution within victim environments, making detection challenging.
Deep Dive Into Technique
Adversaries exploit the Office Test sub-technique by manipulating specific registry keys designed for internal testing and debugging purposes within Microsoft Office applications. These registry keys are typically located under:
HKEY_CURRENT_USER\Software\Microsoft\Office test\Special\PerfHKEY_CURRENT_USER\Software\Microsoft\Office test\Special\Perf\ExcelHKEY_CURRENT_USER\Software\Microsoft\Office test\Special\Perf\Word
When configured, these registry keys can point to malicious DLL files. Upon startup, Office applications such as Word, Excel, or PowerPoint automatically load and execute the referenced DLL, thus enabling attackers to run arbitrary code persistently and covertly.
Key technical details include:
Requires modification of registry keys to point to attacker-controlled DLL files.
DLL payloads typically executed in the context of the current user.
Often employed through initial access vectors such as phishing emails, malicious macros, or compromised software installers.
Does not require administrative privileges if registry keys are modified within
HKEY_CURRENT_USERscope.Difficult to detect without specialized monitoring, as these keys are rarely audited or reviewed during routine security checks.
When this Technique is Usually Used
Attackers commonly leverage the Office Test sub-technique in the following scenarios and stages of an attack:
Persistence Stage: Attackers frequently use this sub-technique to ensure their malicious payload executes each time a user opens an Office application, thus maintaining long-term persistence.
Privilege Escalation and Lateral Movement: While it primarily serves persistence, attackers may also use this technique after initial compromise to facilitate lateral movement or privilege escalation by loading payloads that interact with other systems or escalate privileges.
Stealth and Evasion: Due to the uncommon usage and lack of monitoring of Office Test registry keys, attackers exploit this sub-technique to evade detection mechanisms that typically monitor more common persistence methods.
Targeted Attacks and Espionage Campaigns: Sophisticated threat actors often use this technique in targeted attacks and espionage campaigns where stealth and persistence are critical.
How this Technique is Usually Detected
Detecting this sub-technique typically involves monitoring and auditing registry modifications and DLL loading behaviors. Effective detection methods include:
Registry Monitoring:
Monitor creation or modification of registry keys under:
HKEY_CURRENT_USER\Software\Microsoft\Office test\Special\PerfHKEY_CURRENT_USER\Software\Microsoft\Office test\Special\Perf\ExcelHKEY_CURRENT_USER\Software\Microsoft\Office test\Special\Perf\Word
Use endpoint detection and response (EDR) tools or SIEM solutions to alert on suspicious registry key modifications.
DLL Load Monitoring:
Employ application whitelisting or DLL monitoring tools to detect unexpected DLL loading by Office applications.
Monitor Office application processes (Word.exe, Excel.exe, PowerPoint.exe) for loading DLLs from unusual or temporary file locations.
Behavioral Analysis:
Implement behavioral detection rules in EDR tools to identify anomalous behavior associated with Office startup, especially unexpected DLL loads or unusual process spawning.
Indicators of Compromise (IoCs):
Suspicious registry values pointing to DLL files in temporary directories or user-specific folders.
Unusual DLL file names or paths loaded by Office applications.
Correlation of registry key modifications with known malicious activity timestamps.
Why it is Important to Detect This Technique
Early detection of the Office Test sub-technique is crucial due to its potential impacts and stealthy nature. Key reasons include:
Persistent Access: Attackers can maintain long-term persistence through automatic execution upon Office application startup, allowing ongoing compromise and data exfiltration.
Stealthy Execution: The technique is rarely monitored, enabling attackers to remain undetected for extended periods, increasing the risk of extensive damage.
Privilege Escalation and Lateral Movement: Persistent access can facilitate further attacks, including privilege escalation, lateral movement, and execution of additional malicious payloads.
Data Exfiltration and Espionage: Attackers leveraging this technique often target sensitive information, intellectual property, or confidential communications, posing significant risks to organizational security.
Reputation and Compliance Risks: Undetected persistent threats can lead to severe consequences, including data breaches, regulatory violations, financial losses, and reputational damage.
Examples
Real-world examples of adversaries employing this sub-technique include:
APT32 (Ocean Lotus):
Known to leverage Office Test registry keys to persistently execute malicious payloads.
Typically uses spear-phishing emails to initially infect targets, followed by registry key manipulation to maintain long-term access.
Payloads often include custom DLLs designed for espionage and data exfiltration.
FIN7 Cybercrime Group:
Has employed Office Test registry keys to persistently load malicious DLLs as part of their broader attack campaigns targeting financial and retail sectors.
Often combines this persistence method with other tactics such as credential harvesting, privilege escalation, and lateral movement.
Targeted Espionage Campaigns:
Several documented espionage campaigns targeting government, defense, and critical infrastructure sectors have utilized Office Test registry keys to maintain stealthy and persistent access.
Attackers typically place malicious DLLs in user directories or temporary folders, making detection challenging.
Typical attack scenario:
Victim receives a phishing email with a malicious Office document or macro-enabled attachment.
Upon execution, the document or macro modifies Office Test registry keys to reference a malicious DLL.
The malicious DLL is subsequently loaded each time the victim opens Word or Excel, enabling persistent and covert access.
Attackers leverage this persistent access to conduct espionage, data exfiltration, lateral movement, or deployment of additional malware.
Understanding these examples underscores the critical importance of monitoring and detecting this specific sub-technique to protect organizational assets and sensitive information.
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