Renamed PsExec Service Execution

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

Detects suspicious launch of a renamed version of the PSEXESVC service with, which is not often used by legitimate administrators

Known false positives

Legitimate administrative tasks

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique

Telemetry coverage

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

Rule body

title: Renamed PsExec Service Execution
id: 51ae86a2-e2e1-4097-ad85-c46cb6851de4
status: test
description: Detects suspicious launch of a renamed version of the PSEXESVC service with, which is not often used by legitimate administrators
references:
    - https://learn.microsoft.com/en-us/sysinternals/downloads/psexec
    - https://www.youtube.com/watch?v=ro2QuZTIMBM
author: Florian Roth (Nextron Systems)
date: 2022-07-21
tags:
    - attack.execution
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        OriginalFileName: 'psexesvc.exe'
    filter:
        Image: 'C:\Windows\PSEXESVC.exe'
    condition: selection and not filter
falsepositives:
    - Legitimate administrative tasks
level: high

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    OriginalFileName: 'psexesvc.exe'

Stage 2: `not filter`

filter:
    Image: 'C:\Windows\PSEXESVC.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	eq	`C:\Windows\PSEXESVC.exe`	`excludes:Image` `field:"Image" value:"C:\Windows\PSEXESVC.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`OriginalFileName`	eq	`psexesvc.exe` corpus 4 (sigma 3, elastic 1)	`field:"OriginalFileName" kind:eq value:"psexesvc.exe"`