A lot of virus infections (most, actually) come from exploits in out-of-date browser plugins.  A common trick is for nefarious websites to popup messages saying (e.g.) "You must update your Adobe Flash!" and users end up installing toolbars and other garbage into their systems.  Don't fall for it. I had been recommending a page from…

To turn on Tracking Protection in Firefox: Type in about:config in the location bar and hit enter. You’ll see a warning about possibly voiding your warranty. Hit “I’ll be careful, I promise!” to continue. Search for privacy.trackingprotection.enabled. Double-click that to toggle the value to true. A study done with this setting change provided page load…