My friend is able to hack my computer and pretty much do everything he wants to it remotely. He uses some sort of vnc that allows him to get on without permission. Im sure some of it is done through terminal. He is also able to change my password without knowing the original. Im wondering if theres any way that I can possibly block him from having access? or does anyone have any idea of what programs he using? I'm running Linux mint 7 (a variant of ubuntu 9.04) and so is he. He says the software he uses is cross-platform so switching operating systems wont help. Any help would be appreciated.