In order to do a good job of protecting your computer as well as your actions/behavior at free or public wireless hotspots you need to know some basic security facts regarding them:
- It is a network where all computers are sharing the same Internet connection
- Any computer on the wireless hotspot potentially can see the data being sent/received by other computers
The first fact is simple. Anyone with a computer and a wireless network interface can be on the wireless hotspot--especially if it is not secure. "Anyone" could easily be a malicious hacker who collects user login credentials and other private/personal information (e.g. name, address, social security number, birth date, credit card numbers, and so on).
The second fact isn't obvious to most computer users. Network traffic on a wireless network can be read by any computer in that network. There are free tools out there that can tap into the wireless network and capture the data transmissions of all the computers connected to a hotspot. Take a look at this article I wrote on just such a tool called WireShark for Protocol Analysis and Troubleshooting, and read the section on "Be a hacker: Capture login credentials and watch network communications". You will find that it doesn't take much technical skill to tap into a hotspot.