Trust Access Disable For VBApplications

Hunt Hypothesis

Detects registry changes to Microsoft Office “AccessVBOM” to a value of “1” which disables trust access for VBA on the victim machine and lets attackers execute malicious macros without any Microsoft

Detection Rule

Sigma (Original)

title: Trust Access Disable For VBApplications
id: 1a5c46e9-f32f-42f7-b2bc-6e9084db7fbf
related:
    - id: 9b894e57-033f-46cf-b7fa-a52804181973
      type: obsolete
status: test
description: Detects registry changes to Microsoft Office "AccessVBOM" to a value of "1" which disables trust access for VBA on the victim machine and lets attackers execute malicious macros without any Microsoft Office warnings.
references:
    - https://twitter.com/inversecos/status/1494174785621819397
    - https://www.mcafee.com/blogs/other-blogs/mcafee-labs/zloader-with-a-new-infection-technique/
    - https://securelist.com/scarcruft-surveilling-north-korean-defectors-and-human-rights-activists/105074/
author: Trent Liffick (@tliffick), Nasreddine Bencherchali (Nextron Systems)
date: 2020-05-22
modified: 2023-08-17
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Security\AccessVBOM'
        Details: 'DWORD (0x00000001)'
    condition: selection
falsepositives:
    - Unlikely
level: high

KQL (Azure Sentinel)

imRegistry
| where RegistryKey endswith "\\Security\\AccessVBOM" and RegistryValueData =~ "DWORD (0x00000001)"

KQL (Microsoft 365 Defender)

DeviceRegistryEvents
| where RegistryKey endswith "\\Security\\AccessVBOM" and RegistryValueData =~ "DWORD (0x00000001)"

Required Data Sources

False Positive Guidance

• Unlikely

MITRE ATT&CK Context

• Tactic: Persistence
• Technique: T1112 — T1112

References

• https://twitter.com/inversecos/status/1494174785621819397
• https://www.mcafee.com/blogs/other-blogs/mcafee-labs/zloader-with-a-new-infection-technique/
• https://securelist.com/scarcruft-surveilling-north-korean-defectors-and-human-rights-activists/105074/
• SigmaHQ Rule