Plesk can require a separate username and password before serving a directory and anything below it.
Steps
- Open Websites & Domains, then Password-Protected Directories.
- Select Add Protected Directory.
- Enter the path relative to the domain's document root and save it.
- Open the protected directory entry.
- Add at least one user with a unique password.
- Test the directory in a private browser window.
This protects web access to that path. It is not a replacement for application permissions, and it does not encrypt files stored on the server.