T1546.009: AppCert DLLs
Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by AppCert DLLs loaded into processes. Dynamic-link libraries (DLLs) that are specified in the AppCertDLLs
Registry key under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager</code> are loaded into every process that calls the ubiquitously used application programming interface (API) functions
CreateProcess
, CreateProcessAsUser
, CreateProcessWithLoginW
, CreateProcessWithTokenW
, or WinExec
.
Similar to Process Injection, this value can be abused to obtain elevated privileges by causing a malicious DLL to be loaded and run in the context of separate processes on the computer. Malicious AppCert DLLs may also provide persistence by continuously being triggered by API activity.
Positive Technologies products that cover the technique
MaxPatrol SIEM knowledge base
mitre_attck_defense_evasion: PT-CR-1360: Suspicious_Registry_Value: Windows Registry abuse. This is often used by attackers for persistence, privilege escalation, lateral movement, defense evasion, data collection, and other malicious activity. mitre_attck_persistence: PT-CR-1349: AppCert_DLLs_Persist: Persistence by changing AppCertDLLs component settings
Detection
ID | DS0011 | Data source and component | Module: Module Load | Description | Monitor DLL loads by processes, specifically looking for DLLs that are not recognized or not normally loaded into a process. Tools such as Sysinternals Autoruns may overlook AppCert DLLs as an auto-starting location. |
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ID | DS0009 | Data source and component | Process: OS API Execution | Description | Monitor and analyze application programming interface (API) calls that are indicative of Registry edits, such as |
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ID | DS0024 | Data source and component | Windows Registry: Windows Registry Key Modification | Description | Monitor the AppCertDLLs Registry value for modifications that do not correlate with known software, patch cycles, etc. |
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ID | DS0017 | Data source and component | Command: Command Execution | Description | Monitor executed commands and arguments that may establish persistence and/or elevate privileges by executing malicious content triggered by AppCert DLLs loaded into processes. |
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ID | DS0009 | Data source and component | Process: Process Creation | Description | Monitor newly executed processes that may establish persistence and/or elevate privileges by executing malicious content triggered by AppCert DLLs loaded into processes. |
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Mitigation
ID | M1038 | Name | Execution Prevention | Description | Adversaries install new AppCertDLL binaries to execute this technique. Identify and block potentially malicious software executed through AppCertDLLs functionality by using application control tools, like Windows Defender Application Control, AppLocker, or Software Restriction Policies where appropriate. |
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