The Simplenews module simply allows you to create and send newsletters to your contacts.
Drupal has an excellent search engine by keywords, the search module that is provided at the base with Drupal. Multiple search operators can be used, the intersection of keywords (AND), union (OR), negation (NO), and searching for complete sentences. The ranking algorithm considers several factors such as the frequency of the word, its HTML markup, the popularity and date of publication of the content. By being detached from the content update via the cron command, the indexing process does not affect the fast operation of the site. Above all, the engine is very easy to use since it only takes two clicks to activate the module!
The security of a Drupal instance is ensured by the regular update of the core and modules. All updates and their severity can be found on www.drupal.org/security
For example, for Drupal core, a "Highly critical - Remote code execution" alert should induce a core update as soon as possible.