Finger.EXE Execution

Status: test
Severity: high
Log source: product windows, category process_creation
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.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

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

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.

Field	Kind	Values
`Image`	ends_with	`\finger.exe` corpus 8 (sigma 8)
`OriginalFileName`	eq	`finger.exe` corpus 2 (sigma 2)

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Finger.EXE Execution

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Finger.EXE Execution

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`