Security Kit Oct 2nd, 2014 (updated Mar 28th, 2018) "Module provides Drupal installation with various security hardening options. This lets your mitigate the risks of exploitation of different web application vulnerabilities." Read more about Security Kit
Security Review Oct 2nd, 2014 (updated Mar 28th, 2018) "The Security Review module automates testing for many of the easy-to-make mistakes that render your site insecure." Read more about Security Review
Hacked! Feb 24th, 2013 (updated Apr 13th, 2014) This module shows if Drupal or any of its modules have been changed. If you have the Diff module installed, it will show you the exact lines changed. Read more about Hacked!