Installing and Registering a Password Filter DLL

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You can use the Windows password filter to filter domain or local account passwords. To use the password filter for domain accounts, install and register the DLL on each domain controller in the domain.

Perform the following steps to install your password filter. You can perform these steps manually, or you can write an installer to perform these steps. You need to be an Administrator or belong to the Administrator Group to perform these steps.

To install and register a Windows password filter DLL

  1. Copy the DLL to the Windows installation directory on the domain controller or local computer. On standard installations, the default folder is \Windows\System32. Make sure that you create a 32-bit password filter DLL for 32-bit computers and a 64-bit password filter DLL for 64-bit computers, and then copy them to the appropriate location.

  2. To register the password filter, update the following system registry key:

    HKEY_LOCAL_MACHINE
   SYSTEM
      CurrentControlSet
         Control
            Lsa

    If the Notification Packages value of type REG_MULTI_SZ exists, add the name of your DLL to the existing value data. Do not overwrite the existing values, and do not include the .dll extension.

    If the Notification Packages value does not exist, create it, give it the REG_MULTI_SZ type and then specify the name of the DLL for the value data. Do not include the .dll extension.

    The Notification Packages value can add multiple packages.

  3. Find the password complexity setting.

    In Control Panel, click Performance and Maintenance, click Administrative Tools, double-click Local Security Policy, double-click Account Policies, and then double-click Password Policy.

  4. To enforce both the default Windows password filter and the custom password filter, ensure that the Passwords must meet complexity requirements policy setting is enabled. Otherwise, disable the Passwords must meet complexity requirements policy setting.

Password Filter Programming Considerations

Strong Password Enforcement and Passfilt.dll

Password Filter Functions