XScreenSaver is a modular screen saver and locker for X11 containing more than 200 screen savers. This package is used by both xscreensaver and gnome-screensaver.
To install XScreensaver open Synaptic Package Manager and type xscreensaver in the search field. Mark xscreensaver, xscreensaver-gl-extra and xscreensaver-data-extra for installation and click on the Apply button.
or
$sudo apt-get install xscreensaver