ldebrouwer

An up-to-date WordPress installation is as safe as it can be, plugins however can often pose a security risk because they’re not maintained by hundreds of contributors. A plugin is as secure as the security knowledge of the developer allows it to be. In some cases this creates loopholes for exploits. WP Plugin Security Check checks plugins for bad practices and possible security holes limiting the risk of a compromised WordPress installation to a ‘hate to say I told you so’.

WP Plugin Security Check

WP Plugin Security Check checks if your WordPress plugins are 'safe'.

sdesalas

This plugin allows WordPress to block over 95% of spam comments using a time-based hash.
This allows for a minimum sanity check and yet should remove almost all spam comments 
without the need to sign up to any third party APIs.
The plugin has been tested in real world conditions for around 12 months. It will not block 
real comments and it is pretty effective against spam, however it only uses a very simple 
algorithm and for that reason some spam comments may still make it through.

WP Simple SpamCheck

This plugin allows WordPress to block over 95% of spam comments using a time-based hash.

WP Plugin Security Check vs WP Simple SpamCheck