NCSI

Windows check a Microsoft site for connectivity, using the Network Connectivity Status Indicator site. NCSI performs a DNS lookup on www.msftncsi.com and sends a DNS lookup request for dns.msftncsi.com.

You can block this probe by adding the content of the data/<type>/extra.txt hosts file.

But you will have a "No Internet access" warning in your system tray.

To solve this issue you can use the Debian NCSI through NCSI > Apply Debian NCSI:

Then you can test your internet connection the Microsoft way: