Use of Pcalua For Execution

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems), E.M. Anhaus (originally from Atomic Blue Detections, Endgame), oscd.community
Source: github.com/SigmaHQ/sigma

Detects execition of commands and binaries from the context of The program compatibility assistant (Pcalua.exe). This can be used as a LOLBIN in order to bypass application whitelisting.

Known false positives

Legitimate use by a via a batch script or by an administrator.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059` Command and Scripting Interpreter

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Use of Pcalua For Execution
id: 0955e4e1-c281-4fb9-9ee1-5ee7b4b754d2
related:
    - id: fa47597e-90e9-41cd-ab72-c3b74cfb0d02
      type: obsolete
status: test
description: Detects execition of commands and binaries from the context of The program compatibility assistant (Pcalua.exe). This can be used as a LOLBIN in order to bypass application whitelisting.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Pcalua/
    - https://pentestlab.blog/2020/07/06/indirect-command-execution/
author: Nasreddine Bencherchali (Nextron Systems), E.M. Anhaus (originally from Atomic Blue Detections, Endgame), oscd.community
date: 2022-06-14
modified: 2023-01-04
tags:
    - attack.execution
    - attack.t1059
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\pcalua.exe'
        CommandLine|contains: ' -a' # No space after the flag because it accepts anything as long as there a "-a"
    condition: selection
falsepositives:
    - Legitimate use by a via a batch script or by an administrator.
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '\pcalua.exe'
    CommandLine|contains: ' -a'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-a`	`field:"CommandLine" kind:match value:" -a"`
`Image`	ends_with	`\pcalua.exe` corpus 3 (sigma 3)	`field:"Image" kind:ends_with value:"\pcalua.exe"`