Please remember that if someone calls you telling you that you have a problem that you didn’t know about it is probably a scam. As someone who has fixed thousands of computers one thing that I have never done is randomly called someone to ask if they need help. Do random doctors, mechanics, plumbers, or any other service people that you are not familiar with intrude in your life? I hope not. Your IT professional should be put in the same category. When you need service we are there to assist only when you initiate contact.
Check out this article.