"Module provides Drupal installation with various security hardening options. This lets your mitigate the risks of exploitation of different web application vulnerabilities."

"The Security Review module automates testing for many of the easy-to-make mistakes that render your site insecure."

This Drupal 8 module allows to restrict text formats on fields.

"The Paranoia module attempts to identify all the places that a user can evaluate PHP via Drupal's web interface and then block those. It reduces the potential impact of an attacker gaining elevated permission on a Drupal site."

Force users to pick strong passwords.