The Public Wi-Fi Security Risk
By default, macOS is designed to be as helpful as possible when it comes to keeping you connected to the internet. If you walk into a coffee shop, an airport, or a hotel, and your Mac detects an open, unsecured Wi-Fi network (or a network it vaguely remembers from a previous visit years ago), it might automatically attempt to connect to it without asking for your explicit permission. While this seems convenient, it is a significant security risk. Automatically joining unknown or unverified public networks exposes your device to potential man-in-the-middle attacks, packet sniffing, and unauthorized data interception.
How to Disable “Ask to join new networks”
You can configure macOS to only connect to specific, trusted networks that you have explicitly chosen, and ignore everything else in the background.
1. Click the Apple logo () in the top-left corner of your screen.
2. Select System Settings (or System Preferences on older versions of macOS).
3. In the left-hand navigation sidebar, click on Wi-Fi.
4. Scroll down past your current connection to the bottom of the main pane.
5. Look for the toggle switch labelled Ask to join new networks.
6. Turn this toggle Off. (In older macOS versions, this might be a checkbox that you need to uncheck).
When this is disabled, your Mac will only automatically connect to “Known Networks.” If it cannot find a known network, it will simply remain disconnected until you manually click the Wi-Fi icon in the menu bar and select a network yourself.
How to Manage and Forget “Known Networks”
Even with the above setting disabled, your Mac might still automatically connect to a dangerous network if it shares the same name (SSID) as a network you connected to previously (like a generic “Starbucks WiFi”). You must clean out your saved networks.
1. On the same Wi-Fi settings page, scroll to the bottom and click the Advanced… button.
2. You will see a list of every Wi-Fi network your Mac has ever connected to, under the heading “Known Networks.”
3. Scroll through this list. If you see old hotel networks, generic airport hotspots, or networks you do not recognize, select them.
4. Click the small circle with three dots (or the minus button on older OS versions) next to the network name and select Remove From List.
5. Click Remove to confirm.
By purging this list of open, public hotspots, you guarantee your Mac will never automatically connect to them again, ensuring you only join secure, verified networks.