There is finally a Windows server-side solution to prevent “unauthenticated bind” requests (detailed in LDAP RFC 4513 section 5.1.2 with a note regarding the subsequent security considerations in section 6.3.1) from allowing unauthorized users to successfully authenticate.

It has always been possible to handle in code (i.e. verify that username and password are both non-null prior to communicating with the directory server) and is my personal preference as a developer cannot predict how individual directory services will be configured.

But for the third-party apps that don’t prevent unauthenticated binds, a setting to disallow unauthenticated bind operations to Active Directory was added in Windows 2019 — in your Configuration partition, open the properties of CN=Directory Service, CN=Windows NT, CN=Services, CN=Configuration — find the msDS-Other-Settings attribute, and add a new entry DenyUnauthenticatedBind=1