the xscreensaver install bunch of 'hacks' (screensaver programs) and configuration file that lists all of them (visible in xscreensaver-demo, also used when random screensaver is picked). Most of these hacks are installed by xscreensaver but some are not. e.g. electricsheep is neither installed nor is it required or recommended by xscreensaver but it is one of the hacks on the list (in demo). is this a bug? erik