I had a total melt down today freaking out about this , I also surf a lot on it, anyway downloaded the avast security app from the Amazon store and can now sleep easy ...it has anti virus, malweb scanner and even an anti theft device thingy , it runs fine and takes up little memory on your device , so I'd recommend it. there was an article posted in my question below from experts who recommended it.
hope that helps .
hope that helps .