Detection rules › Sigma

Notepad Password Files Discovery

Status
experimental
Severity
low
Log source
category process_creation, product windows
Author
The DFIR Report
Source
github.com/SigmaHQ/sigma

Detects the execution of Notepad to open a file that has the string "password" which may indicate unauthorized access to credentials or suspicious activity.

Known false positives

  • Legitimate use of opening files from remote hosts by administrators or users. However, storing passwords in text readable format could potentially be a violation of the organization's policy. Any match should be investigated further.

MITRE ATT&CK coverage

TacticTechniques
Discovery

Telemetry coverage

Rule body

title: Notepad Password Files Discovery
id: 3b4e950b-a3ea-44d3-877e-432071990709
status: experimental
description: Detects the execution of Notepad to open a file that has the string "password" which may indicate unauthorized access to credentials or suspicious activity.
references:
    - https://thedfirreport.com/2025/02/24/confluence-exploit-leads-to-lockbit-ransomware/
    - https://intel.thedfirreport.com/eventReports/view/57  # Private Report
author: 'The DFIR Report'
tags:
    - attack.discovery
    - attack.t1083
date: 2025-02-21
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        ParentImage|endswith: '\explorer.exe'
        Image|endswith: '\notepad.exe'
        CommandLine|endswith:
        # Note: Commandline to contain a file with the string password and a specific extension
            - 'password*.txt'
            - 'password*.csv'
            - 'password*.doc'
            - 'password*.xls'
    condition: selection
falsepositives:
    - Legitimate use of opening files from remote hosts by administrators or users. However, storing passwords in text readable format could potentially be a violation of the organization's policy. Any match should be investigated further.
level: low

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ParentImage|endswith: '\explorer.exe'
    Image|endswith: '\notepad.exe'
    CommandLine|endswith:
        - 'password*.txt'
        - 'password*.csv'
        - 'password*.doc'
        - 'password*.xls'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
CommandLineends_with
  • password*.csv
  • password*.doc
  • password*.txt
  • password*.xls
field:"CommandLine" kind:ends_with
Imageends_with
  • \notepad.exe corpus 10 (sigma 10)
field:"Image" kind:ends_with value:"\notepad.exe"
ParentImageends_with
  • \explorer.exe corpus 13 (sigma 13)
field:"ParentImage" kind:ends_with value:"\explorer.exe"