What we give away when we log on to a public Wi-Fi network:

We can now see some of the actual internet traffic of those around us. We see that someone with a MacBook is browsing the site Nu.nl. We can see that many devices are sending documents using WeTransfer, some are connecting to Dropbox, and some show activity on Tumblr. We see that someone has just logged on to FourSquare. The name of this person is also shown, and, after googling his name, we recognize him as the person sitting just a few feet away from us.

In the last couple of years, I’ve upgraded my overall data security posture by using unique strong passwords and two-factor authentication whenever possible, but I still use public wifi (maybe not for long) and haven’t started encrypting my email or anonymizing my web traffic. 

I’m far too boring to really need to worry about anyone taking a deliberate interest in my data, but you never know who’s lurking on public wifi.