There are two ways to allow an app through Windows Defender Firewall. Both of them are risky:
- Add an app to the list of allowed apps (less risky).
- Open a port (more risky).
When you add an app to the list of allowed apps in Windows Defender Firewall—sometimes called unblocking—or when you open a Windows Defender Firewall port, you allow a specific app to send info to or from your device through the firewall, as though you drilled a hole in the firewall. This makes your device less secure and might create opportunities for hackers or malware to use one of those openings to get to your files or use your device to spread malware to other devices.
Generally, it's safer to add an app to the list of allowed apps than to open a port. A port stays open until you close it, but an allowed app opens the "hole" only when needed.
To help decrease your security risk:
Only allow an app or open a port when you really need to, and follow the steps to remove apps from the list of allowed apps or close ports that you no longer need.
Never allow an app that you don't recognize to communicate through the firewall.