Define file shares for downloading security intelligence updates: registry value DefinitionUpdateFileSharesSourcesComputerHKLM\Software\Policies\Microsoft\Windows Defender\Signature Updates

Policy ID: SignatureUpdate_DefinitionUpdateFileSharesSources
Scope: Computer Configuration
Supported on: At least Windows Server 2012, Windows 8 or Windows RT
Source: Administrative Templates (.admx) for Windows 11 2026 Update (26H2) (version 1.0)
Category: Windows Components › Microsoft Defender Antivirus › Security Intelligence Updates

Registry

DefinitionUpdateFileSharesSources

REG_SZComputer

HKLM\Software\Policies\Microsoft\Windows Defender\Signature Updates Current key

Enabled value: Depends on the option value
Element: Define file shares for downloading security intelligence updates
Value type: REG_SZ
Required: true

Apply with .reg · CMD · PowerShell

.reg

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows Defender\Signature Updates]

; Value names and types follow the ADMX. Replace <enter value> below with your own data
"DefinitionUpdateFileSharesSources"="<enter value>"

CMD

:: Value names and types follow the ADMX. Replace <enter value> below with your own data

reg add "HKLM\Software\Policies\Microsoft\Windows Defender\Signature Updates" /v "DefinitionUpdateFileSharesSources" /t REG_SZ /d "<enter value>" /f

PowerShell

# Value names and types follow the ADMX. Replace <enter value> below with your own data

New-Item -Path 'HKLM:\Software\Policies\Microsoft\Windows Defender\Signature Updates' -Force | Out-Null
New-ItemProperty -Path 'HKLM:\Software\Policies\Microsoft\Windows Defender\Signature Updates' -Name 'DefinitionUpdateFileSharesSources' -PropertyType String -Value '<enter value>' -Force | Out-Null