Office Template Macros

What the technique is

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. Office Visual Basic for Applications (VBA) macros 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. Shared templates may also be stored and pulled from remote locations. 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. […]

What MITRE says you would watch

• AN1436

  Adversaries inject VBA macros into Office templates such as Normal.dotm or Personal.xlsb or redirect Office template load path via registry key (GlobalDotName) to gain persistence. Template macros trigger execution of malicious code on application startup.

• AN1437

  Malicious VBA macros embedded in base templates like Normal.dotm or Personal.xlsb are automatically loaded and executed at startup. Template path may be hijacked to load a remote or attacker-controlled template via GlobalDotName registry setting.