Bastille is a distribution specific hardening tool. In Debian, the name of the package is just bastille. This tool searches the system for room to improve system security. Note that many of its questions require some understanding of Unix/Linux related concepts. To Bastille’s credit, there is a general explanation of most questions and projected impact of each decision.
While Bastille is a good tool to use, I do not advise the use of it on an existing production system unless tests have been done on a test system.