If another system tries to connect to an app on Mac
When another computer tries to connect to an app on your Mac over the network or internet, macOS displays an alert message. The app may be trying to allow other computers to connect with your Mac, or it may be sharing information with other computers.
Note: If no action is taken, the message remains displayed, and any attempts to connect to the app are denied.
On your Mac, do one of the following:
If this type of behavior is expected from this app, click Allow.
If you don’t expect the app to connect across the network, or if you don’t want to share information, click Deny. This blocks attempts by other systems to connect to the app.