Are you using windows as your operating system ?
If the answer is yes you might want to do this;
1- Click on the Windows Start button, click on "Control Panel", the Control Panel window will open (or in Windows 8, click on "Desktop" from the Windows Start Menu and then click on "Control Panel" when the desktop appears).
2- Click on "System and Security" in the Control Panel.
3 - Click on "System" in the System and Security - Control Panel.
4- Click on Remote settings in the top left of the, System - Control Panel. The small "System Properties" window will open.
5- In the "System Properties" window, click on tab titled "Remote" (if it's not already selected). Then, under "Remote Assistance", untick or remove the tick from "Allow remote connections to this computer". Then,* under "Remote Desktop", tick the radio button (the little circle) on "Don't allow connections to this computer".
*this step doesn't apply to all versions of windows / computers
I am posting this because a neighbour of ours got a phone call from a man who said he was from microsoft, within seconds he had taken control of our neighbours PC & demanded payment to free it, fortunately at this point they realised it was best to put the phone down & have had to pay for it repaired.