Why public Wi-Fi is dangerous
Wi-Fi networks in cafés, airports and hotels are rarely secure. The problems: no encryption or weak encryption (anyone on the network can see your traffic), anyone can set up a fake access point with a similar name ('Starbucks WiFi Free'), hackers use simple tools to intercept data, and the network owner can monitor all your traffic. It is like sending postcards instead of sealed letters.
Man-in-the-middle (MITM) attacks
A MITM attack happens when a hacker intercepts the communication between you and the sites you visit. On public Wi-Fi, the hacker sits between you and the router, captures all your unencrypted traffic, can see your passwords and personal information, can inject malicious content into pages, and you notice nothing. Free tools make this easy, so even beginner hackers can do it.
Data at risk on public Wi-Fi
On an unsecured network, the following can be intercepted: passwords entered on HTTP (non-HTTPS) sites, emails sent and received, unencrypted chat messages, session cookies (which allow impersonation), files you download or upload, and even some HTTPS data if the certificate is compromised. Mobile apps are especially vulnerable because they often have less protection than browsers.
Using public Wi-Fi without protection is like shouting your secrets in a crowded room.
VPN: your best protection
A VPN (Virtual Private Network) creates an encrypted tunnel for all your data. Benefits: all your traffic is encrypted, even on an unsecured network, other users on the network cannot see anything, the network owner sees only that you use a VPN (not the content), and your real IP address is hidden. Recommended VPNs: ProtonVPN (free with limits), Mullvad (very privacy-friendly) and IVPN. Avoid free VPNs (except ProtonVPN), which often sell your data.
Good practices without a VPN
If you must use public Wi-Fi without a VPN: stick to HTTPS sites (check for the padlock), avoid financial transactions and sensitive accounts, turn off file sharing on your device, forget the network after use (so it does not reconnect automatically), use two-factor authentication everywhere, and prefer mobile data for sensitive activity (it is more secure than public Wi-Fi).
Fake access points (Evil Twin)
Hackers create networks with names like 'Airport_Free_WiFi' to trap victims. How to protect yourself: ask staff for the exact name of the official network, be wary of unsecured networks (no password), avoid networks with generic names, do not connect automatically to open networks, and if a network asks you to install a certificate, refuse (it is often an attempted MITM attack). When in doubt, use your mobile data.