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refactor(rules): Improve Activity from unhooked NTDLL module rule #638

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rabbitstack merged 1 commit into from
Mar 4, 2026
Merged

refactor(rules): Improve Activity from unhooked NTDLL module rule #638

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21 changes: 18 additions & 3 deletions rules/defense_evasion_activity_from_unhooked_ntdll_module.yml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name: Activity from unhooked NTDLL module
id: 24f48f6c-9d97-498d-badc-65e179d19599
version: 1.0.0
version: 1.1.0
description: |
Detects suspicious activity originating from an unhooked or manually mapped copy of NTDLL loaded
into a process. This behavior is commonly associated with defense evasion frameworks that bypass
Expand All @@ -21,6 +21,7 @@ condition: >
maxspan 2m
by ps.uuid
|load_dll and
ps.token.integrity_level != 'SYSTEM' and
dll.name ~= 'ntdll.dll' and foreach(thread._callstack, $frame,
$frame.symbol imatches
(
Expand All @@ -35,6 +36,22 @@ condition: >
'?:\\Windows\\System32\\sxwmon64.dll',
'?:\\ProgramData\\Symantec\\Symantec Endpoint Protection\\*\\sysfer.dll'
) and
ps.exe not imatches
(
'?:\\Windows\\Microsoft.NET\\Framework\\*\\ngen.exe',
'?:\\Windows\\Microsoft.NET\\Framework64\\*\\ngen.exe',
'?:\\Windows\\Microsoft.NET\\Framework\\*\\mscorsvw.exe',
'?:\\Windows\\Microsoft.NET\\Framework64\\*\\mscorsvw.exe',
'?:\\Windows\\servicing\\TrustedInstaller.exe',
'?:\\Program Files (x86)\\Microsoft Visual Studio\\Installer\\vswhere.exe',
'?:\\Program Files\\Microsoft Visual Studio\\Installer\\vswhere.exe',
'?:\\Program Files (x86)\\Microsoft\\EdgeUpdate\\MicrosoftEdgeUpdate.exe',
'?:\\Program Files\\Microsoft\\EdgeUpdate\\MicrosoftEdgeUpdate.exe',
'?:\\Program Files\\Adobe\\Acrobat DC\\Acrobat\\RDCNotificationClient\\FullTrustNotifier.exe',
'?:\\Program Files (x86)\\Adobe\\Acrobat DC\\Acrobat\\RDCNotificationClient\\FullTrustNotifier.exe',
'?:\\Program Files (x86)\\Common Files\\Adobe\\ARM\\*\\AdobeARM.exe',
'?:\\Program Files\\Common Files\\Adobe\\ARM\\*\\AdobeARM.exe'
) and
count(ps.modules, '?:\\*ntdll.dll') >= 2 and
not foreach(thread._callstack, $frame, $frame.module imatches ('?:\\Windows\\Sys*\\ntdll.dll') and $frame.allocation_size > 0)
|
Expand All @@ -43,8 +60,6 @@ condition: >
(create_file) or
(set_thread_context) or
(create_remote_thread) or
(open_process) or
(open_thread) or
(set_value) or
(rename_file) or
(delete_file)) and
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