Q: How Can I Find Out If Someone Is Spying On My Macbook?

How can I find out if someone is spying on my macbook?  It's about 5  years old and I think someone is remotely controlling it even though my remote management and screen sharing is always off in the Sharing panel in Systems Preferences.   I don't SHARE anything willingly!  My screen shakes up and down or sometimes it just falls a few inches and I keep losing my place.  This only happens while I am on the internet.  The arrow icon for the mouse also behaves erratically at times, as if it is being controlled by someone else.  And I have people stalking me who seem to know what I buy on the internet and where I am going when I use google maps, ect....   How do I get rid of remote desktop from a MAC 10.6.8  or trace the idiots doing this to me??? 

Thanks.