hell yes they can they did it to mine, by the name of cadam, how I do not know, but he could see everything I was doing, and then a message came up on the screen saying "say byebye to your computer, cadam has hacked into your system" so I turned it off and when I rebooted, it just never worked again, and messages came up on the startup screen saying stuff like "cadam.. remember that" and really abusive stuff. Had to buy a whole new computer in the end :-S