To prevent emails from accidentally getting sent from a local development environment, I use a two part scheme. First, for Drupal, I turn on the devel module and then add the following to my settings.php:

How I block trackers and ads

Password security rainbow table module for Drupal.

"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."

Here is a copy of an archived article which was removed from the net but that I find very useful for security reviews.

Here's how to use Mollom on your custom form (according to http://kahthong.com/2013/06/integrate-your-custom-drupal-forms-mollom-captcha-spam-protection)

In this example, we add the print_mail_form from the print module to Mollum's list of available forms to protect.

Make spam go away! This is a great service that is free for a low traffic site. A great anti-spam solution for Drupal! Also check out Honeypot and the Bad Behavior module.

The Log Filter module for Drupal extends the core Database Log (dblog) module.