You Never Know Who's Watching on Cafe Wi-Fi
Cafes, airports, hotels, shopping malls - free Wi-Fi is everywhere. Connecting to a password-free Wi-Fi network is convenient, but have you ever thought about what's happening behind the scenes?
Using free Wi-Fi means connecting to the same network as strangers. And technically, traffic on the same network can be intercepted.
What Can Happen on Free Wi-Fi
Traffic Eavesdropping (Packet Sniffing)
Unencrypted traffic can be read by other users connected to the same Wi-Fi. If a site uses HTTPS encryption, the communication content is protected, but on HTTP (unencrypted) sites, passwords and messages you enter are visible in plain text.
Fortunately, most major sites now support HTTPS, so this risk has decreased compared to before. If you see a lock icon in your browser's address bar, the communication is encrypted.
Fake Wi-Fi Hotspots (Evil Twin Attack)
The most dangerous threat is the "Evil Twin" attack. An attacker sets up a Wi-Fi hotspot with a name that looks just like the real one, such as "Starbucks_WiFi_Free." When users connect to the fake Wi-Fi, all their traffic passes through the attacker.
Even on HTTPS sites, the attacker can see "which sites you accessed" (domain names). While the communication content is encrypted, DNS queries are often unencrypted.
Session Hijacking
An attack that steals your logged-in session information (cookies) and impersonates you to access services. While the risk has decreased with HTTPS adoption, it remains dangerous on HTTP sites.
Tips for Using Free Wi-Fi Safely
- Check for HTTPS: Look for the lock icon in the address bar. Don't enter personal information on sites without it
- Use a VPN: Encrypts all your traffic, making it safe to communicate even on free Wi-Fi. The most effective countermeasure
- Turn off auto-connect: Your smartphone's feature to automatically reconnect to previously used Wi-Fi networks increases the risk of Evil Twin attacks. Review your smartphone privacy settings to disable this
- Avoid online banking and important logins: If absolutely necessary, switch to your mobile data connection (4G/5G)
- Turn off file sharing: Disable AirDrop and Windows network sharing on public Wi-Fi
- Use "Forget": After you're done, select "Forget This Network" in your Wi-Fi settings
Why Is Free Wi-Fi "Free"?
The reasons cafes and hotels offer free Wi-Fi go beyond simple customer service.
- Customer attraction: "Wi-Fi available" is a reason to visit, especially important for nomad workers and remote workers
- Extended stay time: Wi-Fi availability extends visit duration, leading to additional orders
- Data collection: Some operators require email addresses or social media accounts at connection time for marketing purposes. For a deeper look at how public Wi-Fi networks expose your data, the risks extend beyond just eavesdropping
- Terms of service consent: The terms displayed at connection time may include "consent to collection of browsing data"
There's always a reason behind "free." Take a moment to check the terms of service before connecting to Wi-Fi.
Summary
Free Wi-Fi is convenient, but there's a risk of traffic being intercepted by other users on the same network. While HTTPS adoption has reduced the risk, practice using a VPN, turning off auto-connect, and avoiding sensitive operations. Check your IP address on IP Check-san while connected to free Wi-Fi, and you'll see a different IP address than usual.