Look at the URL (address field) when you are at Facebook.
If it says http and not https you do not have secure surfing, and you can more easily be hacked.
Change this. Go to: Account > Account settings > Account Security and check the box for https. Press Save to store settings.
Voila! Now you surf on a secure platform. Facebook choose http automatically and you must choose the https manually to make it work.
But remember that if you get virus you can still get hacked, so do not click on stupid links and addons. Share this with all of your friends and let them surf secure too!