If you're like me, whenever you're at a coffee shop, or anyplace else that offers free WiFi, you probably take advantage of that and connect your phone. While the free WiFi isn't always faster than my 4G cell phone service, connecting to WiFi makes sure I don't impact my cell phone plan's data quota, and some apps and downloads will only work on WiFi. So what's the problem?
When you connect any device to a WiFi, you're connecting your system to that network, and potentially making your system visible and vulnerable to other devices on the same network. I won't bore you with the technical details of how that can happen, but the fact is, it's a possibility.