RegAsm.exe

  • File Path: C:\WINDOWS\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe
  • Description: Microsoft .NET Assembly Registration Utility
  • Comments: Flavor=Retail

Hashes

Type Hash
MD5 15D0F3ABFB5A3E38E83EA61A082EF934
SHA1 9FF4A64E44EFDCD088DFE489466ED612FFF1EF55
SHA256 1136010A4706295F80343FE364D90D5789288DEAD5AB0ED0E0981D29AD669BBC
SHA384 26D8D84ADE0755C8FDF6E3CCEAA525DD9F5033E5FE5ADA1A6D47EF530410D0190F4F5046C2D91E79CA6C535B18412F41
SHA512 B33AA91069382A2F57275FBAE3CD94BF477C13AB263EE07A94422DA9BC3D43513DF4016449D103953D87CA672BA9E5F83D854D17E9228E865F5C1753466EEA5B
SSDEEP 768:D8XcJiMjm2ieHFYPyCsSuJbn8dBhF+iSMH6Iq8ASYDKcagxW6l:PYMaNyFYPYSAb8dBndH+lDKcaL6l
PESHA1 0450D0707FF7734EA1C66BABBF16810586D45E2F
PE256 2AF324A5DF399003923593F9FFCE376A4DBED4F44FF3AB93EDEEF2D022AC3843

Runtime Data

Usage (stdout):

Microsoft .NET Framework Assembly Registration Utility version 4.8.4161.0
for Microsoft .NET Framework version 4.8.4161.0
Copyright (C) Microsoft Corporation.  All rights reserved.

Syntax: RegAsm AssemblyName [Options]
Options:
    /unregister          Unregister types
    /tlb[:FileName]      Export the assembly to the specified type library
                         and register it
    /regfile[:FileName]  Generate a reg file with the specified name
                         instead of registering the types. This option
                         cannot be used with the /u or /tlb options
    /codebase            Set the code base in the registry
    /registered          Only refer to already registered type libraries
    /asmpath:Directory   Look for assembly references here
    /nologo              Prevents RegAsm from displaying logo
    /silent              Silent mode. Prevents displaying of success messages
    /verbose             Displays extra information
    /? or /help          Display this usage message

Usage (stderr):

RegAsm : error RA0000 : Failed to load 'C:\WINDOWS\system32\help' because it is not a valid .NET assembly

Loaded Modules:

Path
C:\WINDOWS\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe
C:\WINDOWS\System32\KERNEL32.dll
C:\WINDOWS\System32\KERNELBASE.dll
C:\WINDOWS\SYSTEM32\MSCOREE.DLL
C:\WINDOWS\SYSTEM32\ntdll.dll

Signature

  • Status: Signature verified.
  • Serial: 33000002ED2C45E4C145CF48440000000002ED
  • Thumbprint: 312860D2047EB81F8F58C29FF19ECDB4C634CF6A
  • Issuer: CN=Microsoft Windows Production PCA 2011, O=Microsoft Corporation, L=Redmond, S=Washington, C=US
  • Subject: CN=Microsoft Windows, O=Microsoft Corporation, L=Redmond, S=Washington, C=US

File Metadata

  • Original Filename: RegAsm.exe
  • Product Name: Microsoft .NET Framework
  • Company Name: Microsoft Corporation
  • File Version: 4.8.4161.0 built by: NET48REL1
  • Product Version: 4.8.4161.0
  • Language: English (United States)
  • Legal Copyright: Microsoft Corporation. All rights reserved.
  • Machine Type: 64-bit

File Scan

  • VirusTotal Detections: 0/73
  • VirusTotal Link: https://www.virustotal.com/gui/file/1136010a4706295f80343fe364d90d5789288dead5ab0ed0e0981d29ad669bbc/detection

File Similarity (ssdeep match)

File Score
C:\Windows\Microsoft.NET\Framework\v4.0.30319\RegAsm.exe 72
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\RegAsm.exe 86
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe 80

Possible Misuse

The following table contains possible examples of RegAsm.exe being misused. While RegAsm.exe is not inherently malicious, its legitimate functionality can be abused for malicious purposes.

Source Source File Example License
sigma win_bad_opsec_sacrificial_processes.yml - https://docs.microsoft.com/en-us/dotnet/framework/tools/regasm-exe-assembly-registration-tool DRL 1.0
sigma win_bad_opsec_sacrificial_processes.yml Image\|endswith: '\regasm.exe' DRL 1.0
sigma win_bad_opsec_sacrificial_processes.yml CommandLine\|endswith: '\regasm.exe' DRL 1.0
sigma win_possible_applocker_bypass.yml - '\regasm.exe' DRL 1.0
LOLBAS Regasm.yml Name: Regasm.exe  
LOLBAS Regasm.yml - Command: regasm.exe AllTheThingsx64.dll  
LOLBAS Regasm.yml - Command: regasm.exe /U AllTheThingsx64.dll  
LOLBAS Regasm.yml - Path: C:\Windows\Microsoft.NET\Framework\v2.0.50727\regasm.exe  
LOLBAS Regasm.yml - Path: C:\Windows\Microsoft.NET\Framework64\v2.0.50727\regasm.exe  
LOLBAS Regasm.yml - Path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\regasm.exe  
LOLBAS Regasm.yml - Path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\regasm.exe  
LOLBAS Regasm.yml - IOC: regasm.exe executing dll file  
LOLBAS Regasm.yml - Link: https://pentestlab.blog/2017/05/19/applocker-bypass-regasm-and-regsvcs/  
LOLBAS Regsvcs.yml Description: Regsvcs and Regasm are Windows command-line utilities that are used to register .NET Component Object Model (COM) assemblies  
LOLBAS Regsvcs.yml - Link: https://pentestlab.blog/2017/05/19/applocker-bypass-regasm-and-regsvcs/  
atomic-red-team index.md - T1218.009 Regsvcs/Regasm MIT License. © 2018 Red Canary
atomic-red-team index.md - Atomic Test #1: Regasm Uninstall Method Call Test [windows] MIT License. © 2018 Red Canary
atomic-red-team windows-index.md - T1218.009 Regsvcs/Regasm MIT License. © 2018 Red Canary
atomic-red-team windows-index.md - Atomic Test #1: Regasm Uninstall Method Call Test [windows] MIT License. © 2018 Red Canary
atomic-red-team matrix.md | | | | | Regsvcs/Regasm | | | | | | | | MIT License. © 2018 Red Canary
atomic-red-team windows-matrix.md | | | | | Regsvcs/Regasm | | | | | | | | MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md # T1218.009 - Regsvcs/Regasm MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md <blockquote>Adversaries may abuse Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Regsvcs and Regasm are Windows command-line utilities that are used to register .NET Component Object Model (COM) assemblies. Both are digitally signed by Microsoft. (Citation: MSDN Regsvcs) (Citation: MSDN Regasm) MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md Both utilities may be used to bypass application control through use of attributes within the binary to specify code that should be run before registration or unregistration: [ComRegisterFunction] or [ComUnregisterFunction] respectively. The code with the registration and unregistration attributes will be executed even if the process is run under insufficient privileges and fails to execute. (Citation: LOLBAS Regsvcs)(Citation: LOLBAS Regasm)</blockquote> MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md - Atomic Test #1 - Regasm Uninstall Method Call Test MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md ## Atomic Test #1 - Regasm Uninstall Method Call Test MIT License. © 2018 Red Canary
atomic-red-team T1218.009.md C:\Windows\Microsoft.NET\Framework\v4.0.30319\regasm.exe /U #{output_file} MIT License. © 2018 Red Canary
signature-base apt_oilrig_oct17.yar $s2 = “C:\Windows\Microsoft.NET\Framework\v2.0.50727\RegAsm.exe” fullword wide CC BY-NC 4.0

MIT License. Copyright (c) 2020-2021 Strontic.