The Unwanted Connection
macOS is designed to be as seamless as possible when it comes to networking. If you connect to a Wi-Fi network at a coffee shop, hotel, or airport and enter the password, macOS remembers that network permanently. By default, the next time you are physically within range of that specific network, your Mac will automatically attempt to connect to it in the background. While this is perfect for your home network, it is a massive security risk if your Mac automatically joins an unencrypted public network at a mall without your explicit permission, potentially exposing your traffic to local snooping.
Managing Known Networks
To protect your privacy and stop macOS from automatically connecting to previously saved Wi-Fi networks without your permission, you must adjust the auto-join settings for each specific network.
Click the Apple logo in the top-left corner and select System Settings. In the left-hand navigation sidebar, click on Wi-Fi. In the main panel, scroll down past your current active connection and click the Advanced… button at the bottom. You will see a list labelled “Known Networks,” showing every Wi-Fi network your Mac has ever joined. Find the specific network you want to stop connecting to (e.g., “Starbucks WiFi”). Click the small circle with three dots (…) next to the network name. In the drop-down menu, you will see a setting labelled Auto-Join with a checkmark next to it. Click Auto-Join to uncheck it. Your Mac will still remember the password, but it will wait for you to manually click the network name before connecting.