Adversaries may abuse Regsvr32.exe to proxy execution of malicious code. Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. The Regsvr32.exe binary may also be signed by Microsoft. (Citation: Microsoft Regsvr32)
Malicious usage of Regsvr32.exe may avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of allowlists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe can also be used to specifically bypass application control using functionality to load COM scriptlets to execute DLLs under user permissions. Since Regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed. (Citation: LOLBAS Regsvr32) This variation of the technique is often referred to as a "Squiblydoo" and has been used in campaigns targeting governments. (Citation: Carbon Black Squiblydoo Apr 2016) (Citation: FireEye Regsvr32 Targeting Mongolian Gov)
Regsvr32.exe can also be leveraged to register a COM Object used to establish persistence via Component Object Model Hijacking. (Citation: Carbon Black Squiblydoo Apr 2016)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| DE.AE-02.01 | Event analysis and detection | Mitigates | T1218.010 | Regsvr32 |
Comments
This diagnostic statement provides for implementation of methods to block similar future attacks via security tools such as antivirus and IDS/IPS to provide protection against threats and exploitation attempts.
References
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| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| CA-07 | Continuous Monitoring | mitigates | T1218.010 | Regsvr32 | |
| SI-10 | Information Input Validation | mitigates | T1218.010 | Regsvr32 | |
| SI-07 | Software, Firmware, and Information Integrity | mitigates | T1218.010 | Regsvr32 | |
| SI-04 | System Monitoring | mitigates | T1218.010 | Regsvr32 |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| action.hacking.variety.Abuse of functionality | Abuse of functionality. | related-to | T1218.010 | Regsvr32 |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| google_secops | Google Security Operations | technique_scores | T1218.010 | Regsvr32 |
Comments
Google Security Ops is able to trigger an alert based on suspicious behavior in Windows with the use of regsvr32.exe and a possible fileless attack via this executable.
This technique was scored as minimal based on low or uncertain detection coverage factor.
https://github.com/chronicle/detection-rules/blob/783e0e5947774785db1c55041b70176deeca6f46/soc_prime_rules/threat_hunting/windows/ole_controls_registered_via_regsvr32_exe__sysmon_behavior.yaral
https://github.com/chronicle/detection-rules/blob/783e0e5947774785db1c55041b70176deeca6f46/soc_prime_rules/ioc_sigma/process_creation/fileless_attack_via_regsvr32_exe.yaral
References
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