Office Application Startup: Макрос в шаблоне
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.
Примеры процедур |
|
| Название | Описание |
|---|---|
| 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) |
Контрмеры |
|
| Контрмера | Описание |
|---|---|
| Behavior Prevention on Endpoint |
Use capabilities to prevent suspicious behavior patterns from occurring on endpoint systems. This could include suspicious process, file, API call, etc. behavior. |
| Disable or Remove Feature or Program |
Remove or deny access to unnecessary and potentially vulnerable software to prevent abuse by adversaries. |
Обнаружение
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)
Ссылки
- Soutcast. (2018, September 14). Outlook Today Homepage Persistence. Retrieved February 5, 2019.
- Parisi, T., et al. (2017, July). Using Outlook Forms for Lateral Movement and Persistence. Retrieved February 5, 2019.
- Shukrun, S. (2019, June 2). Office Templates and GlobalDotName - A Stealthy Office Persistence Technique. Retrieved August 26, 2019.
- Hexacorn. (2017, April 17). Beyond good ol’ Run key, Part 62. Retrieved July 3, 2017.
- Nelson, M. (2014, January 23). Maintaining Access with normal.dotm. Retrieved July 3, 2017.
- Austin, J. (2017, June 6). Getting Started with VBA in Office. Retrieved July 3, 2017.
- Microsoft. (n.d.). Change the Normal template (Normal.dotm). Retrieved July 3, 2017.
- Mavis, N. (2020, September 21). The Art and Science of Detecting Cobalt Strike. Retrieved April 6, 2021.
- 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.
- Reaqta. (2017, November 22). A dive into MuddyWater APT targeting Middle-East. Retrieved May 18, 2020.
- Knowles, W. (2017, April 21). Add-In Opportunities for Office Persistence. Retrieved July 3, 2017.
Связанные риски
Каталоги
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