Cab File Extraction Via Wusa.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects execution of the "wusa.exe" (Windows Update Standalone Installer) utility to extract cab using the "/extract" argument that is no longer supported.

Known false positives

The "extract" flag still works on older 'wusa.exe' versions, which could be a legitimate use (monitor the path of the cab being extracted)

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique

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: Cab File Extraction Via Wusa.EXE
id: 59b39960-5f9d-4a49-9cef-1e4d2c1d0cb9
related:
    - id: c74c0390-3e20-41fd-a69a-128f0275a5ea
      type: derived
status: test
description: |
    Detects execution of the "wusa.exe" (Windows Update Standalone Installer) utility to extract cab using the "/extract" argument that is no longer supported.
references:
    - https://web.archive.org/web/20180331144337/https://www.fireeye.com/blog/threat-research/2018/03/sanny-malware-delivery-method-updated-in-recently-observed-attacks.html
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-04
modified: 2024-08-15
tags:
    - attack.execution
    - detection.threat-hunting
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\wusa.exe'
        CommandLine|contains: '/extract:'
    condition: selection
falsepositives:
    - The "extract" flag still works on older 'wusa.exe' versions, which could be a legitimate use (monitor the path of the cab being extracted)
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '\wusa.exe'
    CommandLine|contains: '/extract:'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/extract:` corpus 2 (sigma 2)	`field:"CommandLine" kind:match value:"/extract:"`
`Image`	ends_with	`\wusa.exe` corpus 4 (sigma 4)	`field:"Image" kind:ends_with value:"\wusa.exe"`