type: attack-pattern
spec_version: 2.1
id: attack-pattern--68f7e3a1-f09f-4164-9a62-16b648a0dd5a
created: 2017-05-31T21:31:26.966Z
created_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
revoked: yes
external_references: source_name: mitre-attack
url: https://attack.mitre.org/techniques/T1117
external_id: T1117
source_name: Microsoft Regsvr32
description: Microsoft. (2015, August 14). How to use the Regsvr32 tool and troubleshoot Regsvr32 error messages. Retrieved June 22, 2016.
url: https://support.microsoft.com/en-us/kb/249873
source_name: LOLBAS Regsvr32
description: LOLBAS. (n.d.). Regsvr32.exe. Retrieved July 31, 2019.
url: https://lolbas-project.github.io/lolbas/Binaries/Regsvr32/
source_name: Carbon Black Squiblydoo Apr 2016
description: Nolen, R. et al.. (2016, April 28). Threat Advisory: “Squiblydoo” Continues Trend of Attackers Using Native OS Tools to “Live off the Land”. Retrieved April 9, 2018.
url: https://www.carbonblack.com/2016/04/28/threat-advisory-squiblydoo-continues-trend-of-attackers-using-native-os-tools-to-live-off-the-land/
source_name: FireEye Regsvr32 Targeting Mongolian Gov
description: Anubhav, A., Kizhakkinan, D. (2017, February 22). Spear Phishing Techniques Used in Attacks Targeting the Mongolian Government. Retrieved February 24, 2017.
url: https://www.fireeye.com/blog/threat-research/2017/02/spear_phishing_techn.html
object_marking_refs: marking-definition--fa42a846-8d90-4e51-bc29-71d5b4802168
modified: 2025-10-24T17:48:53.906Z
name: Regsvr32
description: 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 can be used to execute arbitrary binaries. (Citation: Microsoft Regsvr32)

Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of whitelists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe is also a Microsoft signed binary.

Regsvr32.exe can also be used to specifically bypass process whitelisting 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](https://attack.mitre.org/techniques/T1122). (Citation: Carbon Black Squiblydoo Apr 2016)
kill_chain_phases: kill_chain_name: mitre-attack
phase_name: defense-evasion
kill_chain_name: mitre-attack
phase_name: execution
x_mitre_attack_spec_version: 3.2.0
x_mitre_contributors: Casey Smith
x_mitre_deprecated: no
x_mitre_domains: enterprise-attack
x_mitre_is_subtechnique: no
x_mitre_modified_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
x_mitre_platforms: Windows
x_mitre_version: 1.3