Finger.EXE Execution

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Florian Roth (Nextron Systems), omkar72, oscd.community
Source: github.com/SigmaHQ/sigma

Detects execution of the "finger.exe" utility. Finger.EXE or "TCPIP Finger Command" is an old utility that is still present on modern Windows installation. It Displays information about users on a specified remote computer (typically a UNIX computer) that is running the finger service or daemon. Due to the old nature of this utility and the rareness of machines having the finger service. Any execution of "finger.exe" can be considered "suspicious" and worth investigating.

Known false positives

Admin activity (unclear what they do nowadays with finger.exe)

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Finger.EXE Execution
id: af491bca-e752-4b44-9c86-df5680533dbc
related:
    - id: c082c2b0-525b-4dbc-9a26-a57dc4692074
      type: similar
    - id: 2fdaf50b-9fd5-449f-ba69-f17248119af6
      type: similar
status: test
description: |
    Detects execution of the "finger.exe" utility.
    Finger.EXE or "TCPIP Finger Command" is an old utility that is still present on modern Windows installation. It Displays information about users on a specified remote computer (typically a UNIX computer) that is running the finger service or daemon.
    Due to the old nature of this utility and the rareness of machines having the finger service. Any execution of "finger.exe" can be considered "suspicious" and worth investigating.
references:
    - https://twitter.com/bigmacjpg/status/1349727699863011328?s=12
    - https://app.any.run/tasks/40115012-a919-4208-bfed-41e82cb3dadf/
    - http://hyp3rlinx.altervista.org/advisories/Windows_TCPIP_Finger_Command_C2_Channel_and_Bypassing_Security_Software.txt
author: Florian Roth (Nextron Systems), omkar72, oscd.community
date: 2021-02-24
modified: 2024-06-27
tags:
    - attack.command-and-control
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - OriginalFileName: 'finger.exe'
        - Image|endswith: '\finger.exe'
    condition: selection
falsepositives:
    - Admin activity (unclear what they do nowadays with finger.exe)
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_finger_execution/info.yml

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

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

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\finger.exe` corpus 8 (sigma 8)	`field:"Image" kind:ends_with value:"\finger.exe"`
`OriginalFileName`	eq	`finger.exe` corpus 2 (sigma 2)	`field:"OriginalFileName" kind:eq value:"finger.exe"`