Someone is accessing my computer through remote desktop. How can i block that? I have a mac book pro 8gb i5 core. While I was using a cam service online. Someone send me a link and I opened it by accident. Such link opened another window which appeared to load,but it never did. It send me back to the main page,then next thing i know it open up my desktops as if i had pressed f3, and I never pressed it.

I downloaded Sophos thinking it was a virus, ran it and it did not find anything. I figured it had to be someone controlling my computer for there is no other way to do that with the Dashboard.
How can i block that? because now it happens randomly, and whenever it does my computer gets super slow. Help!
Uncheck 'Remote Management' in System Preferences -> Sharing