Short answer : Yes .. you better use firewall (with anti-spoofing technology) and antivirus Long answer : There id wide range of attacks that can be preformed through WIFI . The impact of those attacks varies from knowing the pages you've visited to getting your password and \ or gaining access over your computer . Attacks like : 1-[Man in the middle][1] 2-[Session hijacking][2] 3-Exploiting a vulnerability in an application you have using [Metasploit][3] 4-use your shared folders to infect your PC with a worm and\or virus . What you can do : 1- Try to encrypt your traffic (use [HTTPS everywhere][4] ) 2- use good security solution like [Eset smart security][5] 3- Configure your WIFI Access point so it can reject non trusted connections (MAC filtering ?) [1]: http://en.wikipedia.org/wiki/Man-in-the-middle_attack [2]: http://en.wikipedia.org/wiki/Session_hijacking [3]: http://en.wikipedia.org/wiki/Metasploit_Project [4]: https://www.eff.org/https-everywhere [5]: http://www.eset.com