Office Persistence via WLL Add-in Dropped to Word STARTUP Folder

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1137Office Application Startup
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects a .wll Word add-in written to the Microsoft Word STARTUP folder, the persistence mechanism used by the PortDoor backdoor against the Russian defense sector. Word automatically loads WLL add-ins from this folder at launch, giving attackers stealthy code execution on every Word start.

Reporting behind it

Related detections9 linkedT1137 — drag to rearrange

Malicious NotDoor Outlook VBA Persistence via VbaProject.OTM Deployment (via process_creation)

Malicious NotDoor Outlook Macro Auto-Execution Enablement via Registry (via registry_set)

Windows Registry Changes for Outlook Task/Note Reminder Trigger

Windows: Suspicious Outlook VbaProject.OTM Macro File Created

Windows Office Startup Folder File Drop for Persistence via Office Documents

Windows Registry: IE ZoneMap Domain Zone Change via ZoneMap\Domains

Windows Registry Set to Hide File Extensions via Explorer Advanced Keys

Windows Registry Changes to Outlook Security Settings

Windows Persistence: Outlook LoadMacroProviderOnBoot Registry Setting Modification

Office Persistence via WLL Add-in Dropped to Word STARTUP Folder

Pivot detection · T1137 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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