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I have just installed a new app on Windows 10. When this app tries to connect to the internet the connection is blocked if Microsoft Defender Firewall is enabled and is not blocked if it's disabled. I don't understand why this happens because I understand outgoing connections are not blocked by default.

I added a rule to Microsoft Defender Firewall to enable connections on both public and private networks, however the rule didn't help.

I've tried to use Event Viewer to find an event that Microsoft Defender Firewall might create when it blocks the connection. I've read that such an event would be created in Event Viewer >> Applications and Services Logs >> Microsoft >> Windows >> Windows Defender >> Operational. However no event is created there.

Can you advise me on how to troubleshoot and/or fix this?

Thank you

John Cashew
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1 Answers1

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Here's a few things to note:

  • Whether outbound connections are allowed by default depends on the respective setting. To check that, start the "Windows Defender Firewall with Advanced Security" Console, select the root element of the tree at the left side, choose "Action -> Properties" from the menu and note the "Outbound connections" dropdown button. Note that there are three tabs in that dialog for Domain, Public and Private Profiles.

  • Even if outbound connections are allowed by default, certain apps, ports, ip addresses and so on can be blocked individually. To check that, start the "Windows Defender Firewall with Advanced Security" Console and click on "Outbound rules" at the left side. Check whether there are any rules that block connections.

  • Note also that network / firewall problems might be complex and not visible at the first sight. As a very simple example, suppose that your app is not blocked by the firewall, but that the app needs to communicate with a certain DNS server which is blocked by the firewall. In this case, your app would fail because it would not be able to resolve host names to IP addresses, but there would be no rule in the firewall that blocks the app itself.

Binarus
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