Well the first thing i ever do to any computer system i own is to uninstall anything Macafee, nortons or any other 3rd party stuff like that.
I make sure the firewall that comes with windows is active, install Microsoft Secruity Essentials. Install Spybot, Malwarebytes and Ccleaner. Regularily scan usingnall these tools and NEVER have an issue.
However, the choice is yours to make.
I can only suggest that you google for issues like yours and read the results to see if there is a similar trend forming and actnon the solutions suggested.
Best of luck.
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