Almost everyone who uses Windows has seen it. You launch an application or a game. The Windows Firewall appears and indicates that some features of this application are "blocked". What does it mean and should you allow access?
Why does this message appear?
This message appears when an application wants to act as a server and accept incoming connections. This prompt does not appear for most applications you use, such as web browsers and email clients. You only see it in certain types of applications, such as media servers, games with multiplayer features, online file sharing tools, and other server applications.
Windows Firewall blocks incoming connections by default. But the first time that it blocks connections to a new application, this message appears. You can then choose to allow the connection or not. This ensures that connections are not silently blocked without your knowledge.
On Windows 10, a popup window "The Windows Defender Firewall has blocked some features of this application" is displayed. On Windows 7 and 8, you see instead the message "The Windows Firewall has blocked some features of this application."
Should you allow access?
When this box appears, you have some choices. You can click "Allow Access" and allow incoming connections through the firewall. Or, you can click "Cancel" and the firewall continues to block incoming connections for this application.
You can also choose the types of networks on which you want to allow connections. For example, you can allow a media server application only on private networks. So when you connect your laptop to the public Wi-Fi network, no one can connect to your media server. People in your home or office network will still be able to connect.
When you connect to a network, you choose to set it as public or private …Windows does not automatically know. You can change this option for a network later in the Control Panel or Settings application.
If you trust an application and want to use all its features, you must allow access. If you prohibit access to a PC game, you may not be able to host multiplayer games. If this prompt appears and you want to use a media server to share your media content with other systems on your network, you will probably need to allow access to do so. A BitTorrent client, for example, needs this access to download data to other systems on the Internet.
If you do not allow access, an application may not work properly. For example, you may not be able to host multiplayer games in a PC game because the firewall blocks incoming connections.
If you do not recognize the app, you can search the name on the web and get more information. Some types of malware works as a server and can trigger a firewall alert. Run a scan with your favorite antivirus program if you are concerned that your PC is infected with malware.
How to allow or prohibit access later
Windows Firewall does not prompt you for the same application twice, but you can change the setting to allow or deny any application later. To do this, go to Control Panel> System and Security> Windows Defender Firewall> Allow an application or feature through the Windows Defender firewall.
Click "Change Settings" to unlock the settings. Find the application in the list, and then select the Public or Private checkboxes to determine whether it is allowed or not. If you uncheck the two boxes next to an application, it will not be allowed to connect to public or private networks. If you check both boxes, the app can connect to both.
How to disable notifications
If you prefer not to see these notifications and Windows automatically blocks incoming connections to all applications, you can do so.
To do this, go to Control Panel> System and Security> Windows Defender Firewall> Change Notification Settings.
To disable notifications, uncheck the option "Notify me when Windows Defender Firewall blocks a new application." There are two options here: one for private networks and one for public networks.
This window is pretty common on Windows and you will usually have an idea of why an application wants this level of network access. In most cases, if you trust an application, you can safely enable it. Even if you allow an application through the Windows Firewall, the router Network Address Translation (NAT) always prevents many incoming connections unless you configure port forwarding.