Office Application Startup: Office Template Macros
Other sub-techniques of Office Application Startup (6)
Adversaries may abuse Microsoft Office templates to obtain persistence on a compromised system. Microsoft Office contains templates that are part of common Office applications and are used to customize styles. The base templates within the application are used each time an application starts. (Citation: Microsoft Change Normal Template)
Office Visual Basic for Applications (VBA) macros (Citation: MSDN VBA in Office) can be inserted into the base template and used to execute code when the respective Office application starts in order to obtain persistence. Examples for both Word and Excel have been discovered and published. By default, Word has a Normal.dotm template created that can be modified to include a malicious macro. Excel does not have a template file created by default, but one can be added that will automatically be loaded.(Citation: enigma0x3 normal.dotm)(Citation: Hexacorn Office Template Macros) Shared templates may also be stored and pulled from remote locations.(Citation: GlobalDotName Jun 2019)
Word Normal.dotm location:
C:\Users\<username>\AppData\Roaming\Microsoft\Templates\Normal.dotm
Excel Personal.xlsb location:
C:\Users\<username>\AppData\Roaming\Microsoft\Excel\XLSTART\PERSONAL.XLSB
Adversaries may also change the location of the base template to point to their own by hijacking the application's search order, e.g. Word 2016 will first look for Normal.dotm under C:\Program Files (x86)\Microsoft Office\root\Office16\, or by modifying the GlobalDotName registry key. By modifying the GlobalDotName registry key an adversary can specify an arbitrary location, file name, and file extension to use for the template that will be loaded on application startup. To abuse GlobalDotName, adversaries may first need to register the template as a trusted document or place it in a trusted location.(Citation: GlobalDotName Jun 2019)
An adversary may need to enable macros to execute unrestricted depending on the system or enterprise security policy on use of macros.
Procedure Examples |
|
| Name | Description |
|---|---|
| MuddyWater |
MuddyWater has used a Word Template, Normal.dotm, for persistence.(Citation: Reaqta MuddyWater November 2017) |
| BackConfig |
BackConfig has the ability to use hidden columns in Excel spreadsheets to store executable files or commands for VBA macros.(Citation: Unit 42 BackConfig May 2020) |
| Cobalt Strike |
Cobalt Strike has the ability to use an Excel Workbook to execute additional code by enabling Office to trust macros and execute code without user permission.(Citation: Talos Cobalt Strike September 2020) |
Mitigations |
|
| Mitigation | Description |
|---|---|
| Behavior Prevention on Endpoint |
Behavior Prevention on Endpoint refers to the use of technologies and strategies to detect and block potentially malicious activities by analyzing the behavior of processes, files, API calls, and other endpoint events. Rather than relying solely on known signatures, this approach leverages heuristics, machine learning, and real-time monitoring to identify anomalous patterns indicative of an attack. This mitigation can be implemented through the following measures: Suspicious Process Behavior: - Implementation: Use Endpoint Detection and Response (EDR) tools to monitor and block processes exhibiting unusual behavior, such as privilege escalation attempts. - Use Case: An attacker uses a known vulnerability to spawn a privileged process from a user-level application. The endpoint tool detects the abnormal parent-child process relationship and blocks the action. Unauthorized File Access: - Implementation: Leverage Data Loss Prevention (DLP) or endpoint tools to block processes attempting to access sensitive files without proper authorization. - Use Case: A process tries to read or modify a sensitive file located in a restricted directory, such as /etc/shadow on Linux or the SAM registry hive on Windows. The endpoint tool identifies this anomalous behavior and prevents it. Abnormal API Calls: - Implementation: Implement runtime analysis tools to monitor API calls and block those associated with malicious activities. - Use Case: A process dynamically injects itself into another process to hijack its execution. The endpoint detects the abnormal use of APIs like `OpenProcess` and `WriteProcessMemory` and terminates the offending process. Exploit Prevention: - Implementation: Use behavioral exploit prevention tools to detect and block exploits attempting to gain unauthorized access. - Use Case: A buffer overflow exploit is launched against a vulnerable application. The endpoint detects the anomalous memory write operation and halts the process. |
| Disable or Remove Feature or Program |
Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries. This involves identifying software or features that are no longer needed or that could be exploited and ensuring they are either removed or properly disabled. This mitigation can be implemented through the following measures: Remove Legacy Software: - Use Case: Disable or remove older versions of software that no longer receive updates or security patches (e.g., legacy Java, Adobe Flash). - Implementation: A company removes Flash Player from all employee systems after it has reached its end-of-life date. Disable Unused Features: - Use Case: Turn off unnecessary operating system features like SMBv1, Telnet, or RDP if they are not required. - Implementation: Disable SMBv1 in a Windows environment to mitigate vulnerabilities like EternalBlue. Control Applications Installed by Users: - Use Case: Prevent users from installing unauthorized software via group policies or other management tools. - Implementation: Block user installations of unauthorized file-sharing applications (e.g., BitTorrent clients) in an enterprise environment. Remove Unnecessary Services: - Use Case: Identify and disable unnecessary default services running on endpoints, servers, or network devices. - Implementation: Disable unused administrative shares (e.g., C$, ADMIN$) on workstations. Restrict Add-ons and Plugins: - Use Case: Remove or disable browser plugins and add-ons that are not needed for business purposes. - Implementation: Disable Java and ActiveX plugins in web browsers to prevent drive-by attacks. |
Detection
Many Office-related persistence mechanisms require changes to the Registry and for binaries, files, or scripts to be written to disk or existing files modified to include malicious scripts. Collect events related to Registry key creation and modification for keys that could be used for Office-based persistence.(Citation: CrowdStrike Outlook Forms)(Citation: Outlook Today Home Page) Modification to base templates, like Normal.dotm, should also be investigated since the base templates should likely not contain VBA macros. Changes to the Office macro security settings should also be investigated.(Citation: GlobalDotName Jun 2019)
References
- Soutcast. (2018, September 14). Outlook Today Homepage Persistence. Retrieved February 5, 2019.
- Shukrun, S. (2019, June 2). Office Templates and GlobalDotName - A Stealthy Office Persistence Technique. Retrieved August 26, 2019.
- Parisi, T., et al. (2017, July). Using Outlook Forms for Lateral Movement and Persistence. Retrieved February 5, 2019.
- Nelson, M. (2014, January 23). Maintaining Access with normal.dotm. Retrieved July 3, 2017.
- Microsoft. (n.d.). Change the Normal template (Normal.dotm). Retrieved July 3, 2017.
- Hexacorn. (2017, April 17). Beyond good ol’ Run key, Part 62. Retrieved July 3, 2017.
- Austin, J. (2017, June 6). Getting Started with VBA in Office. Retrieved July 3, 2017.
- Reaqta. (2017, November 22). A dive into MuddyWater APT targeting Middle-East. Retrieved May 18, 2020.
- Hinchliffe, A. and Falcone, R. (2020, May 11). Updated BackConfig Malware Targeting Government and Military Organizations in South Asia. Retrieved June 17, 2020.
- Microsoft. (2021, July 2). Use attack surface reduction rules to prevent malware infection. Retrieved June 24, 2021.
- Knowles, W. (2017, April 21). Add-In Opportunities for Office Persistence. Retrieved November 17, 2024.
- Mavis, N. (2020, September 21). The Art and Science of Detecting Cobalt Strike. Retrieved September 12, 2024.
Связанные риски
Каталоги
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