I scanned my whole computer using the Avast Free Antivirus and since then, every browser in my Windows 7 is showing many of the trusted sites “Not Secure”. I tried reinstalling the windows 7. But even after a fresh installation, still those sites are Not Secure. Those sites are actually secure but I think Avast has deleted some SSL authorities from Windows who verify the SSL certificates of those sites! But I don’t understand why a fresh installation is also returning the same issue! Is there something Avast done with my motherboard/BIOS?