I've been testing AVG FREE for a while now and they recently released a new version: 8.5
There used to be a time when you couldn't get free antivirus software. Now, you can select from several different vendors. AVG is probably one of the most popular. Another one is called Avira and the other popular software product is made by Avast.
Notice how all these names begin with the letter A?
In any case, if you're interested in using free antivirus software, make sure you read things carefully as you click to download and install the software. You can easily click on the wrong link and before you know it, you'll be entering your credit card information to purchase the "deluxe" or "full" version that includes various bells and whistles. A long time ago, I used to use Norton Antivirus. I don't use Norton anymore because it's caused more problems for me and it drains all my system resources. Bottom line: it really slows my system. When you're dealing with slow machines like ultra-mobile PCs, you need to conserve your resources so that your device doesn't freeze up all the time.