T1218.010 Regsvr32 Mappings

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. Regsvr32.exe is also a Microsoft signed binary. (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" attack 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®

Mappings

Capability ID Capability Description Mapping Type ATT&CK ID ATT&CK Name
CA-7 Continuous Monitoring Protects T1218.010 Regsvr32
SI-10 Information Input Validation Protects T1218.010 Regsvr32
SI-4 System Monitoring Protects T1218.010 Regsvr32
SI-7 Software, Firmware, and Information Integrity Protects T1218.010 Regsvr32
action.hacking.variety.Abuse of functionality Abuse of functionality related-to T1218.010 Signed Binary Proxy Execution: Regsvr32