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Detection rules › Sigma

Network Connection Initiated via Finger.EXE

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

Detects network connections via finger.exe, 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 network connections can also help identify potential malicious infrastructure used by threat actors

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 3Network connection

Rule body yaml

title: Network Connection Initiated via Finger.EXE
id: 2fdaf50b-9fd5-449f-ba69-f17248119af6
related:
    - id: c082c2b0-525b-4dbc-9a26-a57dc4692074
      type: similar
    - id: af491bca-e752-4b44-9c86-df5680533dbc
      type: similar
status: experimental
description: |
    Detects network connections via finger.exe, 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 network connections can also help identify potential malicious infrastructure used by threat actors
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:
    category: network_connection
    product: windows
detection:
    selection:
        Initiated: 'true'
        Image|endswith: '\finger.exe'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Initiated: 'true'
    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)
Initiatedeq
  • true corpus 50 (sigma 50)