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Detection rules › Sigma

DNS Query by Finger Utility

Status
experimental
Severity
high
Log source
product windows, category dns_query
Author
Swachchhanda Shrawan Poudel (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects DNS queries made by the finger utility, which can be abused by threat actors to retrieve remote commands for execution on Windows devices. In one ClickFix malware campaign, adversaries leveraged the finger protocol to fetch commands from a remote server. Since the finger utility is not commonly used in modern Windows environments, its presence already raises suspicion. Investigating such DNS queries can also help identify potential malicious infrastructure used by threat actors for command and control (C2) communication.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1059.003 Command and Scripting Interpreter: Windows Command Shell
Command & ControlT1071.004 Application Layer Protocol: DNS

Event coverage

ProviderEventTitle
SysmonEvent ID 22DNSEvent (DNS query)

Rule body yaml

title: DNS Query by Finger Utility
id: c082c2b0-525b-4dbc-9a26-a57dc4692074
related:
    - id: 2fdaf50b-9fd5-449f-ba69-f17248119af6
      type: similar
    - id: af491bca-e752-4b44-9c86-df5680533dbc
      type: similar
status: experimental
description: |
    Detects DNS queries made by the finger utility, which can be abused by threat actors to retrieve remote commands for execution on Windows devices.
    In one ClickFix malware campaign, adversaries leveraged the finger protocol to fetch commands from a remote server.
    Since the finger utility is not commonly used in modern Windows environments, its presence already raises suspicion.
    Investigating such DNS queries can also help identify potential malicious infrastructure used by threat actors for command and control (C2) communication.
references:
    - https://www.bleepingcomputer.com/news/security/decades-old-finger-protocol-abused-in-clickfix-malware-attacks/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-19
tags:
    - attack.command-and-control
    - attack.t1071.004
    - attack.execution
    - attack.t1059.003
logsource:
    product: windows
    category: dns_query
detection:
    selection:
        Image|endswith: '\finger.exe'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith: '\finger.exe'

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
  • \finger.exe corpus 8 (sigma 8)