What changed
A decade ago much of the web traveled unencrypted, and anyone on the same coffee shop network could read it. Today almost all sites and apps use HTTPS, which encrypts the connection between your device and the service. A snoop on the same network can generally see which sites you visit, not what you do there. That is a privacy leak, not a catastrophe, and the old advice never to touch public WiFi is out of date.
The risks that remain
The main one is the evil twin, a hotspot set up by a stranger with a plausible name, such as the name of the hotel with the word guest after it. Ask the staff for the exact network name rather than picking the strongest signal. A login page that asks for more than a room number or an email address, such as a card number or your email password, is a reason to disconnect.
- Do not click through a browser warning about an invalid certificate on public WiFi, because that warning is the system catching an interception.
- Turn off file sharing and device discovery, and choose the public network profile if your computer asks.
- Turn off automatic joining for open networks, and forget the network when you leave, so your phone does not reconnect to anything with the same name later.
- Use your phone's own hotspot for banking and tax filing if you would rather not think about any of this.
Public charging ports
Federal agencies have warned about juice jacking, in which a tampered USB port pushes malware or copies data while it charges. Documented cases are rare, and current phones default to charging only, asking permission before any data moves. The warnings are still worth heeding because the fix is free. A USB cable carries both power and data, and a wall outlet carries only power.
What to carry
Bring your own wall adapter and cable and plug into an ordinary outlet. A small battery pack solves the airport problem entirely. If a public USB port is the only option, a charge-only cable or a data blocker, which is a small adapter that costs a few dollars, physically disconnects the data pins. If the phone ever asks whether to trust the device it is plugged into, the answer in a public place is no.
Tip A cable you find left behind in a charging station or handed out free at an event is the one to avoid, since a cable itself can be modified and looks identical to a normal one.
