Sigma rule: Suspicious Access to Sensitive File Extensions

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-bce57fe411a4, updated 2025-10-17T00:00:00.000Z.

Rule

Title
Suspicious Access to Sensitive File Extensions
Status
test
Level
medium
Author
Samir Bousseaden
Date
2019-04-03
Modified
2025-10-17
File
rules/windows/builtin/security/win_security_susp_raccess_sensitive_fext.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects known sensitive file extensions accessed on a network share

Log source

product
windows
service
security

Detection

selection:
    EventID: 5145
    RelativeTargetName|endswith:
        - '.bak'
        - '.dmp'
        - '.edb'
        - '.kirbi'
        - '.msg'
        - '.nsf'
        - '.nst'
        - '.oab'
        - '.ost'
        - '.pst'
        - '.rdp'
        # - '\groups.xml'  # Commented out: groups.xml is accessed legitimately by Group Policy processing; high FP rate in enterprise environments
condition: selection

False positives (as the rule lists them)

  • Help Desk operator doing backup or re-imaging end user machine or backup software
  • Users working with these data types or exchanging message files

Tags

  • attack.collection
  • attack.t1039

MITRE ATT&CK ids this rule names

Related rules

References

  • Internal Research

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/builtin/security/win_security_susp_raccess_sensitive_fext.yml

Sources and licences

  • SigmaHQ

    "Suspicious Access to Sensitive File Extensions" by Samir Bousseaden (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/builtin/security/win_security_susp_raccess_sensitive_fext.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Suspicious Access to Sensitive File Extensions",
entity page, dataset version ref-bce57fe411a4, updated 2025-10-17T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/91c945bc-2ad1-4799-a591-4d00198a1215 (accessed 2026-11-03).
Underlying source: SigmaHQ rule 91c945bc-2ad1-4799-a591-4d00198a1215, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.