Signed Binary Proxy Execution: Regsvr32

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. [1]

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. [2] This variation of the technique is often referred to as a "Squiblydoo" attack and has been used in campaigns targeting governments. [3] [4]

Regsvr32.exe can also be leveraged to register a COM Object used to establish persistence via Component Object Model Hijacking. [3]

ID: T1218.010
Sub-technique of:  T1218
Tactic: Defense Evasion
Platforms: Windows
Permissions Required: Administrator, User
Data Sources: Loaded DLLs, Process command-line parameters, Process monitoring, Windows Registry
Defense Bypassed: Anti-virus, Application control, Digital Certificate Validation
Contributors: Casey Smith
Version: 1.0
Created: 23 January 2020
Last Modified: 20 June 2020

Procedure Examples

Name Description

APT19 used Regsvr32 to bypass application control techniques.[26]


APT32 created a Scheduled Task/Job that used regsvr32.exe to execute a COM scriptlet that dynamically downloaded a backdoor and injected it into memory. The group has also used regsvr32 to run their backdoor.[23][24][25]


Astaroth can be loaded through regsvr32.exe.[17]

Blue Mockingbird

Blue Mockingbird has executed custom-compiled XMRIG miner DLLs using regsvr32.exe.[32]

Cobalt Group

Cobalt Group has used regsvr32.exe to execute scripts.[27][28][29]

Deep Panda

Deep Panda has used regsvr32.exe to execute a server variant of Derusbi in victim networks.[22]


Derusbi variants have been seen that use Registry persistence to proxy execution through regsvr32.exe.[16]


Hi-Zor executes using regsvr32.exe called from the Registry Run Keys / Startup Folder persistence mechanism.[14]


Inception has ensured persistence at system boot by setting the value regsvr32 %path%\ctfmonrn.dll /s.[31]


Koadic can use Regsvr32 to execute additional payloads.[12]


Leviathan has used regsvr32 for execution.[13]


More_eggs has used regsvr32.exe to execute the malicious DLL.[19]


Some Orz versions have an embedded DLL known as MockDll that uses Process Hollowing and regsvr32 to execute another payload.[13]

Ragnar Locker

Ragnar Locker has used regsvr32.exe to execute components of VirtualBox.[21]


RogueRobin uses regsvr32.exe to run a .sct file for execution.[18]


Valak has used regsvr32.exe to launch malicious DLLs.[20]


WIRTE has used Regsvr32.exe to trigger the execution of a malicious script.[30]


Xbash can use regsvr32 for executing scripts.[15]


Mitigation Description
Exploit Protection

Microsoft's Enhanced Mitigation Experience Toolkit (EMET) Attack Surface Reduction (ASR) feature can be used to block regsvr32.exe from being used to bypass application control. [5] Identify and block potentially malicious software executed through regsvr32 functionality by using application control [6] tools, like Windows Defender Application Control[7], AppLocker, [8] [9] or Software Restriction Policies [10] where appropriate. [11]


Use process monitoring to monitor the execution and arguments of regsvr32.exe. Compare recent invocations of regsvr32.exe with prior history of known good arguments and loaded files to determine anomalous and potentially adversarial activity. Command arguments used before and after the regsvr32.exe invocation may also be useful in determining the origin and purpose of the script or DLL being loaded. [3]


  1. Microsoft. (2015, August 14). How to use the Regsvr32 tool and troubleshoot Regsvr32 error messages. Retrieved June 22, 2016.
  2. LOLBAS. (n.d.). Regsvr32.exe. Retrieved July 31, 2019.
  3. 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.
  4. Anubhav, A., Kizhakkinan, D. (2017, February 22). Spear Phishing Techniques Used in Attacks Targeting the Mongolian Government. Retrieved February 24, 2017.
  5. National Security Agency. (2016, May 4). Secure Host Baseline EMET. Retrieved June 22, 2016.
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  14. Fidelis Cybersecurity. (2015, December 16). Fidelis Threat Advisory #1020: Dissecting the Malware Involved in the INOCNATION Campaign. Retrieved March 24, 2016.
  15. Xiao, C. (2018, September 17). Xbash Combines Botnet, Ransomware, Coinmining in Worm that Targets Linux and Windows. Retrieved November 14, 2018.
  16. Fidelis Threat Research Team. (2016, May 2). Turbo Twist: Two 64-bit Derusbi Strains Converge. Retrieved August 16, 2018.
  2. Lee, B., Falcone, R. (2019, January 18). DarkHydrus delivers new Trojan that can use Google Drive for C2 communications. Retrieved April 17, 2019.
  3. Villadsen, O.. (2019, August 29). More_eggs, Anyone? Threat Actor ITG08 Strikes Again. Retrieved September 16, 2019.
  4. Salem, E. et al. (2020, May 28). VALAK: MORE THAN MEETS THE EYE . Retrieved June 19, 2020.
  5. SophosLabs. (2020, May 21). Ragnar Locker ransomware deploys virtual machine to dodge security. Retrieved June 29, 2020.
  6. RSA Incident Response. (2014, January). RSA Incident Response Emerging Threat Profile: Shell Crew. Retrieved January 14, 2016.
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  11. Svajcer, V. (2018, July 31). Multiple Cobalt Personality Disorder. Retrieved September 5, 2018.
  12. Gorelik, M. (2018, October 08). Cobalt Group 2.0. Retrieved November 5, 2018.
  13. Giagone, R., Bermejo, L., and Yarochkin, F. (2017, November 20). Cobalt Strikes Again: Spam Runs Use Macros and CVE-2017-8759 Exploit Against Russian Banks. Retrieved March 7, 2019.
  14. S2 Grupo. (2019, April 2). WIRTE Group attacking the Middle East. Retrieved May 24, 2019.
  15. GReAT. (2014, December 10). Cloud Atlas: RedOctober APT is back in style. Retrieved May 8, 2020.
  16. Lambert, T. (2020, May 7). Introducing Blue Mockingbird. Retrieved May 26, 2020.