Windows Event Log Access Tampering Via Registry

 1title: Windows Event Log Access Tampering Via Registry
 2id: ba226dcf-d390-4642-b9af-b534872f1156
 3status: experimental
 4description: |
 5        Detects changes to the Windows EventLog channel permission values. It focuses on changes to the Security Descriptor Definition Language (SDDL) string, as modifications to these values can restrict access to specific users or groups, potentially aiding in defense evasion by controlling who can view or modify a event log channel. Upon execution, the user shouldn't be able to access the event log channel via the event viewer or via utilities such as "Get-EventLog" or "wevtutil".
 6references:
 7    - https://www.atomicredteam.io/atomic-red-team/atomics/T1562.002#atomic-test-8---modify-event-log-channel-access-permissions-via-registry---powershell
 8    - https://www.youtube.com/watch?v=uSYvHUVU8xY
 9    - https://learn.microsoft.com/en-us/windows/win32/secauthz/security-descriptor-definition-language
10author: X__Junior
11date: 2025-01-16
12modified: 2025-08-16
13tags:
14    - attack.privilege-escalation
15    - attack.persistence
16    - attack.defense-evasion
17    - attack.t1547.001
18    - attack.t1112
19logsource:
20    category: registry_set
21    product: windows
22detection:
23    # O:SYG:SYD:(D;;0x1;;;WD)
24    # O:BAG:SYD:(A;;0x2;;;S-1-15-2-1)(D;;0x1;;;WD)
25    selection_key_1:
26        TargetObject|contains: '\SYSTEM\CurrentControlSet\Services\EventLog\'
27        TargetObject|endswith: '\CustomSD'
28    selection_key_2:
29        TargetObject|contains:
30            - '\Policies\Microsoft\Windows\EventLog\'
31            - '\Microsoft\Windows\CurrentVersion\WINEVT\Channels'
32        TargetObject|endswith: '\ChannelAccess'
33    selection_details:
34        - Details|contains: 'D:(D;'
35        - Details|contains|all:
36              - 'D:('
37              - ')(D;'
38    filter_main_trustedinstaller:
39        Image: 'C:\Windows\servicing\TrustedInstaller.exe'
40    filter_main_tiworker:
41        Image|startswith: 'C:\Windows\WinSxS\'
42        Image|endswith: '\TiWorker.exe'
43    filter_optional_empty:
44        Image: ''
45    filter_optional_null:
46        Image: null
47    condition: 1 of selection_key_* and selection_details and not 1 of filter_main_* and not 1 of filter_optional_*
48falsepositives:
49    - Administrative activity, still unlikely
50level: high