detection.wiki

Detection rules › Sigma

Suspicious Binaries and Scripts in Public Folder

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

Detects the creation of a file with a suspicious extension in the public folder, which could indicate potential malicious activity.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1204 User Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

title: Suspicious Binaries and Scripts in Public Folder
id: b447f7de-1e53-4cbf-bfb4-f1f6d0b04e4e
status: experimental
description: Detects the creation of a file with a suspicious extension in the public folder, which could indicate potential malicious activity.
references:
    - https://intel.thedfirreport.com/events/view/30032 # Private Report
    - https://intel.thedfirreport.com/eventReports/view/70 # Private Report
    - https://thedfirreport.com/2025/01/27/cobalt-strike-and-a-pair-of-socks-lead-to-lockbit-ransomware/
author: 'The DFIR Report'
date: 2025-01-23
tags:
    - attack.execution
    - attack.t1204
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|contains: ':\Users\Public\'
        TargetFilename|endswith:
            - '.bat'
            - '.dll'
            - '.exe'
            - '.hta'
            - '.js'
            - '.ps1'
            - '.vbe'
            - '.vbs'
    condition: selection
falsepositives:
    - Administrators deploying legitimate binaries to public folders.
level: high
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_susp_public_folder_extension/info.yml

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    TargetFilename|contains: ':\Users\Public\'
    TargetFilename|endswith:
        - '.bat'
        - '.dll'
        - '.exe'
        - '.hta'
        - '.js'
        - '.ps1'
        - '.vbe'
        - '.vbs'

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
TargetFilenameends_with
  • .bat corpus 17 (sigma 17)
  • .dll corpus 23 (sigma 23)
  • .exe corpus 21 (sigma 20, splunk 1)
  • .hta corpus 13 (sigma 13)
  • .js corpus 9 (sigma 9)
  • .ps1 corpus 17 (sigma 17)
  • .vbe corpus 15 (sigma 15)
  • .vbs corpus 18 (sigma 18)
TargetFilenamematch
  • :\Users\Public\ corpus 2 (sigma 2)