I have a fully patched Windows 10 machine, but I have just been using Windows Defender as I thought it would be better than a free anti-virus like AVG or Avira. I saw on the news sometime ago that a software developer said it's the most secure of the main anti virus solutions. But it now looks like Windows Defender had some security problem last week that could take over machines really easily. What should I do? Do I continue to use Defender, or should I switch to a paid product? If I bought some anti-virus software, would Windows Defender run anyway, so I have two layers of protection?