I have been using Avast antivirus for 2 years. I did not find it useful till now. They say that it is totally free. Bur remember it’s not what they saying. Most of the security features do not work untill you pay the money. After connecting to the internet the adblocjer of the virus do not wrk properly. And the UI of antivirus is very slow it takes much time to load the pages. They improved the design in last update which is quite good. If you add the extension to your browser it prevent many of the sites stays unopen and saying that malware is detected every time. The full scanning option takes too much time about 3hrs even after that viruses still shown in your device. I didn’t find it useful in any way. One should go for Net protector. It works fine and available at cheaper prices