Uncommon Child Process Of Appvlp.EXE

Hunt Hypothesis

Detects uncommon child processes of Appvlp.EXE Appvlp or the Application Virtualization Utility is included with Microsoft Office. Attackers are able to abuse “AppVLP” to execute shell commands. Norma

Detection Rule

Sigma (Original)

title: Uncommon Child Process Of Appvlp.EXE
id: 9c7e131a-0f2c-4ae0-9d43-b04f4e266d43
status: test
description: |
    Detects uncommon child processes of Appvlp.EXE
    Appvlp or the Application Virtualization Utility is included with Microsoft Office. Attackers are able to abuse "AppVLP" to execute shell commands.
    Normally, this binary is used for Application Virtualization, but it can also be abused to circumvent the ASR file path rule folder
    or to mark a file as a system file.
references:
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Appvlp/
author: Sreeman
date: 2020-03-13
modified: 2023-11-09
tags:
    - attack.stealth
    - attack.t1218
    - attack.execution
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\appvlp.exe'
    # Note: Filters based on data from EchoTrail: https://www.echotrail.io/insights/search/appvlp.exe/
    filter_main_generic:
        Image|endswith:
            - ':\Windows\SysWOW64\rundll32.exe'
            - ':\Windows\System32\rundll32.exe'
    filter_optional_office_msoasb:
        Image|contains: ':\Program Files\Microsoft Office'
        Image|endswith: '\msoasb.exe'
    filter_optional_office_skype:
        Image|contains|all:
            - ':\Program Files\Microsoft Office'
            - '\SkypeSrv\'
        Image|endswith: '\SKYPESERVER.EXE'
    filter_optional_office_msouc:
        Image|contains: ':\Program Files\Microsoft Office'
        Image|endswith: '\MSOUC.EXE'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: medium

KQL (Azure Sentinel)

imProcessCreate
| where (ParentProcessName endswith "\\appvlp.exe" or ActingProcessName endswith "\\appvlp.exe") and (not((TargetProcessName endswith ":\\Windows\\SysWOW64\\rundll32.exe" or TargetProcessName endswith ":\\Windows\\System32\\rundll32.exe"))) and (not(((TargetProcessName contains ":\\Program Files\\Microsoft Office" and TargetProcessName endswith "\\msoasb.exe") or ((TargetProcessName contains ":\\Program Files\\Microsoft Office" and TargetProcessName contains "\\SkypeSrv\\") and TargetProcessName endswith "\\SKYPESERVER.EXE") or (TargetProcessName contains ":\\Program Files\\Microsoft Office" and TargetProcessName endswith "\\MSOUC.EXE"))))

Required Data Sources

False Positive Guidance

• Unknown

MITRE ATT&CK Context

• Tactic: Execution
• Technique: T1218 — T1218

References

• https://lolbas-project.github.io/lolbas/OtherMSBinaries/Appvlp/
• SigmaHQ Rule