Detection rules › Sigma
Suspicious Access to Sensitive File Extensions - Zeek
Detects known sensitive file extensions via Zeek
Known false positives
- Help Desk operator doing backup or re-imaging end user machine or backup software
- Users working with these data types or exchanging message files
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Collection | No specific technique |
Rule body
title: Suspicious Access to Sensitive File Extensions - Zeek
id: 286b47ed-f6fe-40b3-b3a8-35129acd43bc
related:
- id: 91c945bc-2ad1-4799-a591-4d00198a1215
type: derived
status: test
description: Detects known sensitive file extensions via Zeek
references:
- Internal Research
author: Samir Bousseaden, @neu5ron
date: 2020-04-02
modified: 2025-10-17
tags:
- attack.collection
logsource:
product: zeek
service: smb_files
detection:
selection:
name|endswith:
- '.pst'
- '.ost'
- '.msg'
- '.nst'
- '.oab'
- '.edb'
- '.nsf'
- '.bak'
- '.dmp'
- '.kirbi'
# - '\groups.xml' # Commented out: groups.xml is accessed legitimately by Group Policy processing; high FP rate in enterprise environments
- '.rdp'
condition: selection
falsepositives:
- Help Desk operator doing backup or re-imaging end user machine or backup software
- Users working with these data types or exchanging message files
level: medium
Stages and Predicates
Stage 0: condition
selectionStage 1: selection
selection:
name|endswith:
- '.pst'
- '.ost'
- '.msg'
- '.nst'
- '.oab'
- '.edb'
- '.nsf'
- '.bak'
- '.dmp'
- '.kirbi'
- '.rdp'
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
name | ends_with |
| field:"name" kind:ends_with |