Hi brannsiu,
You are more vulnerable while using free Wi-Fi because someone can take control of the wifi router or set up a man-in-the-middle attack to gather lots of information from your web browsing.
Here are some of the best things you can do to protect yourself while using free Wi-Fi hotspots:
1) Use a VPN. Personal VPNs create a secure connection between the device and the VPN provider’s Internet gateway which cannot be listened in on.
2) Use secure websites. Don’t transmit any personal or sensitive data, such as social security numbers or credit card numbers, over any URL that is not secure. Look for websites with URLs that start with “https,” which ensures that the communications between your device and the website’s server is encrypted.
3) Keep security software up to date. One of the biggest risks of using a public hotspot is being attacked from the unknown computers sharing the unsecured network. Firewall software, along with antivirus, antiphishing, antimalware, and antispyware software, should be regularly updated.