Registry Modification to Hidden File Extension

Hunt Hypothesis

Hides the file extension through modification of the registry

Detection Rule

Sigma (Original)

title: Registry Modification to Hidden File Extension
id: 5df86130-4e95-4a54-90f7-26541b40aec2
status: test
description: Hides the file extension through modification of the registry
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1112/T1112.md#atomic-test-1---modify-registry-of-current-user-profile---cmd
    - https://unit42.paloaltonetworks.com/ransomware-families/
    - https://www.microsoft.com/en-us/wdsi/threats/malware-encyclopedia-description?name=TrojanSpy%3aMSIL%2fHakey.A
author: frack113
date: 2022-01-22
modified: 2023-08-17
tags:
    - attack.persistence
    - attack.t1137
logsource:
    category: registry_set
    product: windows
detection:
    selection_HideFileExt:
        TargetObject|endswith: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\HideFileExt'
        Details: 'DWORD (0x00000001)'
    selection_Hidden:
        TargetObject|endswith: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Hidden'
        Details: 'DWORD (0x00000002)'
    condition: 1 of selection_*
falsepositives:
    - Administrative scripts
level: medium

KQL (Azure Sentinel)

imRegistry
| where (RegistryKey endswith "\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced\\HideFileExt" and RegistryValueData =~ "DWORD (0x00000001)") or (RegistryKey endswith "\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced\\Hidden" and RegistryValueData =~ "DWORD (0x00000002)")

KQL (Microsoft 365 Defender)

DeviceRegistryEvents
| where (RegistryKey endswith "\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced\\HideFileExt" and RegistryValueData =~ "DWORD (0x00000001)") or (RegistryKey endswith "\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Advanced\\Hidden" and RegistryValueData =~ "DWORD (0x00000002)")

Required Data Sources

False Positive Guidance

• Administrative scripts

MITRE ATT&CK Context

• Tactic: Persistence
• Technique: T1137 — T1137

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1112/T1112.md#atomic-test-1---modify-registry-of-current-user-profile---cmd
• https://unit42.paloaltonetworks.com/ransomware-families/
• https://www.microsoft.com/en-us/wdsi/threats/malware-encyclopedia-description?name=TrojanSpy%3aMSIL%2fHakey.A
• SigmaHQ Rule