detection.wiki

Detection rules › Sigma

Suspicious Creation TXT File in User Desktop

Status
test
Severity
medium
Log source
product windows, category file_event
Author
frack113
Source
github.com/SigmaHQ/sigma

Detects creation of .txt files in user desktop folders via cmd.exe. This behavior may indicate ransomware deploying ransom notes, but can also occur during legitimate administrative tasks. Analysts should investigate for suspicious filenames (e.g., "RANSOM", "DECRYPT", "READ_ME"), bulk file creation patterns, or concurrent encryption activity to determine if this is part of a ransomware attack.

MITRE ATT&CK coverage

TacticTechniques
ImpactT1486 Data Encrypted for Impact

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

title: Suspicious Creation TXT File in User Desktop
id: caf02a0a-1e1c-4552-9b48-5e070bd88d11
status: test
description: |
    Detects creation of .txt files in user desktop folders via cmd.exe. This behavior may indicate ransomware deploying ransom notes, but can also occur during legitimate administrative tasks.
    Analysts should investigate for suspicious filenames (e.g., "RANSOM", "DECRYPT", "READ_ME"), bulk file creation patterns, or concurrent encryption activity to determine if this is part of a ransomware attack.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1486/T1486.md#atomic-test-5---purelocker-ransom-note
author: frack113
date: 2021-12-26
modified: 2026-01-09
tags:
    - attack.impact
    - attack.t1486
    - detection.threat-hunting
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\cmd.exe'
        TargetFilename|contains|all:
            - '\Users\'
            - '\Desktop\'
        TargetFilename|endswith: '.txt'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith: '\cmd.exe'
    TargetFilename|contains|all:
        - '\Users\'
        - '\Desktop\'
    TargetFilename|endswith: '.txt'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \cmd.exe corpus 130 (sigma 130)
TargetFilenameends_with
  • .txt corpus 3 (sigma 3)
TargetFilenamematch
  • \Desktop\ corpus 3 (sigma 3)
  • \Users\ corpus 2 (sigma 2)