Unusual Access to Windows Outlook Unistore Mail Data by Non-Standard Processes
Alerts when unusual processes access Outlook Unistore (data and UnistoreDB store.vol) file locations on Windows.
- Product
- windows
- Category
- file_access
- Author
- frack113 (SigmaHQ), DRL 1.1
- Published
- 2024-05-10
- Updated
- 2026-07-31
ATT&CK techniques
Defense EvasionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule identifies file access attempts to Windows Outlook mail storage locations under AppData\Local\Comms\Unistore\data and UnistoreDB\store.vol when performed by uncommon process images. Such access may indicate attempts to copy or manipulate mailbox data for credential theft or other data collection. It relies on Windows file access telemetry (Kernel File ETW) that includes the accessing process path and the targeted FileName, using image allow-filters and Defender/Thor exclusions to reduce noise.
Reporting behind it
- darkdefender.medium.comhttps://darkdefender.medium.com/windows-10-mail-app-forensics-39025f5418d2
- github.comhttps://github.com/redcanaryco/atomic-red-team/blob/58496ee3306e6e42a7054d36a94e6eb561ee3081/atomics/T1070.008/T1070.008.md#atomic-test-4---copy-and-modify-mailbox-data-on-windows
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/file/file_access/file_access_win_office_outlook_mail_credential.yml
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No changelog recorded for this version.2026-07-30
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: Unusual Access to Windows Outlook Unistore Mail Data by Non-Standard Processes
id: 65a5d102-5094-4418-8a20-eca5789db9ad
status: test
description: This rule identifies file access attempts to Windows Outlook mail storage locations under AppData\Local\Comms\Unistore\data and UnistoreDB\store.vol when performed by uncommon process images. Such access may indicate attempts to copy or manipulate mailbox data for credential theft or other data collection. It relies on Windows file access telemetry (Kernel File ETW) that includes the accessing process path and the targeted FileName, using image allow-filters and Defender/Thor exclusions to reduce noise.
references:
- https://darkdefender.medium.com/windows-10-mail-app-forensics-39025f5418d2
- https://github.com/redcanaryco/atomic-red-team/blob/58496ee3306e6e42a7054d36a94e6eb561ee3081/atomics/T1070.008/T1070.008.md#atomic-test-4---copy-and-modify-mailbox-data-on-windows
- https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/file/file_access/file_access_win_office_outlook_mail_credential.yml
author: frack113, Huntrule Team
date: 2024-05-10
modified: 2024-07-29
tags:
- attack.stealth
- attack.t1070.008
- detection.threat-hunting
logsource:
category: file_access
product: windows
definition: "Requirements: Microsoft-Windows-Kernel-File ETW provider"
detection:
selection_unistore:
FileName|contains: \AppData\Local\Comms\Unistore\data
selection_unistoredb:
FileName|endswith: \AppData\Local\Comms\UnistoreDB\store.vol
filter_main_system:
Image: System
filter_main_generic:
Image|startswith:
- C:\Program Files (x86)\
- C:\Program Files\
- C:\Windows\system32\
- C:\Windows\SysWOW64\
filter_optional_defender:
Image|startswith: C:\ProgramData\Microsoft\Windows Defender\
Image|endswith:
- \MpCopyAccelerator.exe
- \MsMpEng.exe
filter_optional_thor:
Image|endswith:
- \thor64.exe
- \thor.exe
condition: 1 of selection_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
- Antivirus, Anti-Spyware, Anti-Malware Software
- Backup software
- Legitimate software installed on partitions other than "C:\"
- Searching software such as "everything.exe"
level: low
license: DRL-1.1
related:
- id: fc3e237f-2fef-406c-b90d-b3ae7e02fa8f
type: derived