Unfortunately, they aren’t from Microsoft. They aren’t from any technical support agency or department at all. And worse, they never detected anything on your computer; they just pulled your number up at random and called. They are scammers, and they are out to get everything they can off of you: money, access to your computer, and as much of your financial information as they can. And using this scam, they can get you to hand it over to them without any fuss.
What harm can a scammer do once he’s on your computer? Pretty much anything he wants. He can leave software installed on your computer that lets him monitor everything you do, including your passwords as you enter them into websites. Further, he can take control of your computer whenever he wants, so he can use your computer to log in to websites and make it appear YOU are the one doing so. And if you give him payment for any ‘services’ he performs, you can bet he will keep your credit card information to use whenever he wants.
So how can you protect yourself from this scam? The best way is to simply not allow them access to your computer. If someone calls you up without any warning and says they need access to your computer for any reason, don’t give it to them. Don’t follow their instructions, and certainly do not go to any websites they ask you to, as some websites can install software onto your computer automatically. If you do allow someone access to your computer and later realize they may have been a scammer, stop using it! Use a different computer to go to any websites that deal with your personal information such as Facebook, banking institutions, your email, etc., and change your passwords, especially if you save those passwords on your computer. Then take your computer to a local IT company, such as AD Technology, and have it checked for any hidden software that monitors your computer’s activity.
In short, if someone calls you and says they can detect your computer is doing something it shouldn’t, don’t trust them. If you have reason to believe they may be telling the truth, it’s still better to not do anything they ask right then and there, and instead get a number you can call them back at, then check that the number is for who they say they are.