Potential CVE-2021-44228 Exploitation Attempt - VMware Horizon

Status: test
Severity: high
Log source: category process_creation, product windows
Author: @kostastsale
Source: github.com/SigmaHQ/sigma

Detects potential initial exploitation attempts against VMware Horizon deployments running a vulnerable versions of Log4j.

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

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: Potential CVE-2021-44228 Exploitation Attempt - VMware Horizon
id: 3eb91f0a-0060-424a-a676-59f5fdd75610
status: test
description: |
    Detects potential initial exploitation attempts against VMware Horizon deployments running a vulnerable versions of Log4j.
references:
    - https://portswigger.net/daily-swig/vmware-horizon-under-attack-as-china-based-ransomware-group-targets-log4j-vulnerability
    - https://twitter.com/TheDFIRReport/status/1482078434327244805
    - https://www.pwndefend.com/2022/01/07/log4shell-exploitation-and-hunting-on-vmware-horizon-cve-2021-44228/
author: '@kostastsale'
date: 2022-01-14
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2021-44228
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\ws_TomcatService.exe'
    filter_main_shells:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    ParentImage|endswith: '\ws_TomcatService.exe'

Stage 2: `not filter_main_shells`

filter_main_shells:
    Image|endswith:
        - '\cmd.exe'
        - '\powershell.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`\cmd.exe`	`excludes:Image` `field:"Image" value:"\cmd.exe"`
`Image`	ends_with	`\powershell.exe`	`excludes:Image` `field:"Image" value:"\powershell.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ParentImage`	ends_with	`\ws_TomcatService.exe` corpus 6 (sigma 6)	`field:"ParentImage" kind:ends_with value:"\ws_TomcatService.exe"`