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T1218.010 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. The Regsvr32.exe binary may also be signed by Microsoft. 3

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” and has been used in campaigns targeting governments. 4 1

Regsvr32.exe can also be leveraged to register a COM Object used to establish persistence via Component Object Model Hijacking. 4

Item Value
ID T1218.010
Sub-techniques T1218.001, T1218.002, T1218.003, T1218.004, T1218.005, T1218.007, T1218.008, T1218.009, T1218.010, T1218.011, T1218.012, T1218.013, T1218.014
Tactics TA0005
Platforms Windows
Version 2.1
Created 23 January 2020
Last Modified 21 April 2023

Procedure Examples

ID Name Description
S0622 AppleSeed AppleSeed can call regsvr32.exe for execution.21
G0073 APT19 APT19 used Regsvr32 to bypass application control techniques.43
G0050 APT32 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.373839
S0373 Astaroth Astaroth can be loaded through regsvr32.exe.35
G0108 Blue Mockingbird Blue Mockingbird has executed custom-compiled XMRIG miner DLLs using regsvr32.exe.40
C0015 C0015 During C0015, the threat actors employed code that used regsvr32 for execution.49
G0080 Cobalt Group Cobalt Group has used regsvr32.exe to execute scripts.444546
G0009 Deep Panda Deep Panda has used regsvr32.exe to execute a server variant of Derusbi in victim networks.42
S0021 Derusbi Derusbi variants have been seen that use Registry persistence to proxy execution through regsvr32.exe.15
S0554 Egregor Egregor has used regsvr32.exe to execute malicious DLLs.13
S0568 EVILNUM EVILNUM can run a remote scriptlet that drops a file and executes it via regsvr32.exe.17
S0698 HermeticWizard HermeticWizard has used regsvr32.exe /s /i to execute malicious payloads.34
S0087 Hi-Zor Hi-Zor executes using regsvr32.exe called from the Registry Run Keys / Startup Folder persistence mechanism.20
G0100 Inception Inception has ensured persistence at system boot by setting the value regsvr32 %path%\ctfmonrn.dll /s.41
G0094 Kimsuky Kimsuky has executed malware with regsvr32s.47
S0250 Koadic Koadic can use Regsvr32 to execute additional payloads.12
G0065 Leviathan Leviathan has used regsvr32 for execution.22
S0284 More_eggs More_eggs has used regsvr32.exe to execute the malicious DLL.23
S1047 Mori Mori can use regsvr32.exe for DLL execution.14
C0022 Operation Dream Job During Operation Dream Job, Lazarus Group used regsvr32 to execute malware.50
S0229 Orz Some Orz versions have an embedded DLL known as MockDll that uses Process Hollowing and regsvr32 to execute another payload.22
S0650 QakBot QakBot can use Regsvr32 to execute malicious DLLs.302629282731
S0481 Ragnar Locker Ragnar Locker has used regsvr32.exe to execute components of VirtualBox.16
S0270 RogueRobin RogueRobin uses regsvr32.exe to run a .sct file for execution.36
S1018 Saint Bot Saint Bot has used regsvr32 to execute scripts.2425
S1030 Squirrelwaffle Squirrelwaffle has been executed using regsvr32.exe.19
G0127 TA551 TA551 has used regsvr32.exe to load malicious DLLs.33
S0476 Valak Valak has used regsvr32.exe to launch malicious DLLs.3233
G0090 WIRTE WIRTE has used regsvr32.exe to trigger the execution of a malicious script.48
S0341 Xbash Xbash can use regsvr32 for executing scripts.18

Mitigations

ID Mitigation Description
M1050 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 Control7, AppLocker, 8 9 or Software Restriction Policies 10 where appropriate. 11

Detection

ID Data Source Data Component
DS0017 Command Command Execution
DS0011 Module Module Load
DS0029 Network Traffic Network Connection Creation
DS0009 Process Process Creation

References

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