MITRE ATT&CK Technique
Defense Evasion T1121
Description

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) Adversaries can use Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Both utilities may be used to bypass process whitelisting through use of attributes within the binary to specify code that should be run before registration or unregistration: <code>[ComRegisterFunction]</code> or <code>[ComUnregisterFunction]</code> 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)

Supported Platforms
Windows
Created

April 29, 2026

Last Updated

April 29, 2026

STIX Data
{'created': '2017-05-31T21:31:33.499Z',
 'created_by_ref': 'identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5',
 'description': '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)\n'
                '\n'
                'Adversaries can use Regsvcs and Regasm to proxy execution of '
                'code through a trusted Windows utility. Both utilities may be '
                'used to bypass process whitelisting through use of attributes '
                'within the binary to specify code that should be run before '
                'registration or unregistration: '
                '<code>[ComRegisterFunction]</code> or '
                '<code>[ComUnregisterFunction]</code> 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)',
 'external_references': [{'external_id': 'T1121',
                          'source_name': 'mitre-attack',
                          'url': 'https://attack.mitre.org/techniques/T1121'},
                         {'description': 'Microsoft. (n.d.). Regsvcs.exe (.NET '
                                         'Services Installation Tool). '
                                         'Retrieved July 1, 2016.',
                          'source_name': 'MSDN Regsvcs',
                          'url': 'https://msdn.microsoft.com/en-us/library/04za0hca.aspx'},
                         {'description': 'Microsoft. (n.d.). Regasm.exe '
                                         '(Assembly Registration Tool). '
                                         'Retrieved July 1, 2016.',
                          'source_name': 'MSDN Regasm',
                          'url': 'https://msdn.microsoft.com/en-us/library/tzat5yw6.aspx'},
                         {'description': 'LOLBAS. (n.d.). Regsvcs.exe. '
                                         'Retrieved July 31, 2019.',
                          'source_name': 'LOLBAS Regsvcs',
                          'url': 'https://lolbas-project.github.io/lolbas/Binaries/Regsvcs/'},
                         {'description': 'LOLBAS. (n.d.). Regasm.exe. '
                                         'Retrieved July 31, 2019.',
                          'source_name': 'LOLBAS Regasm',
                          'url': 'https://lolbas-project.github.io/lolbas/Binaries/Regasm/'}],
 'id': 'attack-pattern--215190a9-9f02-4e83-bb5f-e0589965a302',
 'kill_chain_phases': [{'kill_chain_name': 'mitre-attack',
                        'phase_name': 'defense-evasion'},
                       {'kill_chain_name': 'mitre-attack',
                        'phase_name': 'execution'}],
 'modified': '2025-10-24T17:48:30.868Z',
 'name': 'Regsvcs/Regasm',
 'object_marking_refs': ['marking-definition--fa42a846-8d90-4e51-bc29-71d5b4802168'],
 'revoked': True,
 'spec_version': '2.1',
 'type': 'attack-pattern',
 'x_mitre_attack_spec_version': '3.2.0',
 'x_mitre_contributors': ['Casey Smith'],
 'x_mitre_deprecated': False,
 'x_mitre_detection': '',
 'x_mitre_domains': ['enterprise-attack'],
 'x_mitre_is_subtechnique': False,
 'x_mitre_modified_by_ref': 'identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5',
 'x_mitre_platforms': ['Windows'],
 'x_mitre_version': '1.3'}
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