I have noticed that some programs like firefox add-ons automatically update themselves without my notice. I need to restrict such behavior since I am under severe limitation regarding internet usage from my ISP. I have to spend each KB of data upload or download with full justification (the way people use water in desert areas!). I have reconfigured those add-ons and also set ubuntu (10.04) system update-check to once every two-weeks. Are there any other programs in ubuntu 10.04 which may be updating/upgrading itself without my notice?