The Auto-Join Annoyance
By default, Ubuntu’s NetworkManager is configured to be helpful: whenever you successfully connect to a Wi-Fi network, it saves the password and automatically connects you to that specific network whenever you are in range. While great for your secure home network, this is a privacy and security risk for public networks like coffee shops, airports, or hotels. You may only want to use that open network once for a specific task, but Ubuntu will silently re-associate with it every time you pass by in the future, potentially exposing your traffic to local snooping without you realizing you are connected.
Disabling Auto-Connect for Specific Networks
To protect your privacy and stop Ubuntu from automatically connecting to previously known, insecure Wi-Fi networks when you are in range, you must edit the individual profile settings for those networks.
Open the GNOME Settings application and click on the Wi-Fi tab in the left-hand sidebar. Under the “Known Networks” section (you may need to click a button or scroll down to see networks you aren’t currently connected to), find the specific network you want to modify (e.g., “Starbucks WiFi”). Click the gear icon next to its name. A settings dialogue box will appear. In the left-hand menu, select the General tab. Look for the checkbox labeled Connect automatically with priority (or just “Connect automatically”). Uncheck this box. Click the Apply button. Ubuntu will remember the password if you ever want to connect manually, but it will no longer silently auto-join that specific network.