Suspicious PsExec Execution

Status: test
Severity: high
Log source: product windows, service security
Author: Samir Bousseaden
Source: github.com/SigmaHQ/sigma

detects execution of psexec or paexec with renamed service name, this rule helps to filter out the noise if psexec is used for legit purposes or if attacker uses a different psexec client other than sysinternal one

MITRE ATT&CK coverage

Tactic	Techniques
Lateral Movement	`T1021.002` Remote Services: SMB/Windows Admin Shares

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 5145: A network share object was checked to see whether client can be granted desired access.

Rule body

title: Suspicious PsExec Execution
id: c462f537-a1e3-41a6-b5fc-b2c2cef9bf82
status: test
description: detects execution of psexec or paexec with renamed service name, this rule helps to filter out the noise if psexec is used for legit purposes or if attacker uses a different psexec client other than sysinternal one
references:
    - https://web.archive.org/web/20230329171218/https://blog.menasec.net/2019/02/threat-hunting-3-detecting-psexec.html
author: Samir Bousseaden
date: 2019-04-03
modified: 2022-08-11
tags:
    - attack.lateral-movement
    - attack.t1021.002
logsource:
    product: windows
    service: security
    definition: 'The advanced audit policy setting "Object Access > Audit Detailed File Share" must be configured for Success/Failure'
detection:
    selection1:
        EventID: 5145
        ShareName: '\\\\\*\\IPC$' # looking for the string \\*\IPC$
        RelativeTargetName|endswith:
            - '-stdin'
            - '-stdout'
            - '-stderr'
    filter:
        RelativeTargetName|startswith: 'PSEXESVC'
    condition: selection1 and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection1 and not filter

Stage 1: `selection1`

selection1:
    EventID: 5145
    ShareName: '\\\\\*\\IPC$'
    RelativeTargetName|endswith:
        - '-stdin'
        - '-stdout'
        - '-stderr'

Stage 2: `not filter`

filter:
    RelativeTargetName|startswith: 'PSEXESVC'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`RelativeTargetName`	starts_with	`PSEXESVC`	`excludes:RelativeTargetName` `field:"RelativeTargetName" value:"PSEXESVC"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`RelativeTargetName`	ends_with	`-stderr` `-stdin` `-stdout`	`field:"RelativeTargetName" kind:ends_with`
`ShareName`	eq	`\\\\\*\\IPC$` corpus 7 (sigma 7)	`field:"ShareName" kind:eq value:"\\\\\*\\IPC$"`