Spam Prevention

Mollom does a terrific job in catching and preventing spam, although recently some of my sites have still been getting spammed as Mollom isn't catching everything. I have been manually processing uncaught spam and adding the links to my mollom blacklist. This modules allows admins to flag content from content list and add it to a blacklist queue. The queue can be used to choose which links should be added to the sites mollom blacklist.

Simple antispam solution.
Module check comment's text and if strings '

GraphMath CAPTCHA is a graphical version of the well-known Math CAPTCHA, which is part of the CAPTCHA module. In this case the mathematical equation is hidden in an obfuscated image. The amount and types of distortion
and noise can be configured along with the image type, the types and sizes of the fonts used, and color settings.
This module is intended as a submodule of the CAPTCHA module. This module was built using the Image CAPTCHA submodule of the CAPTCHA module.

Installation
Installation is the same as all modules: copy the graphmath_captcha dir into the directory of the CAPTCHA module, or to the modules dir. Enable the module under the category Spam Control, then go to admin/config/people/captcha/graphmath_captcha to configure it.

Requirements

• The main CAPTCHA module
• The GD graphical library
• Truetype font support

This Block Commenter Module will provides a flexible method for Drupal site
administrators to block the list of registered users from commenting
corresponding to selected content types.
Thus it prevents spammers from commenting on the Drupal site.
Watch video demonstration of block commenter
To configure this module,

1. Navigate to 'admin/config/people/block_commenter'.
2. Enter a comma-separated list of users which you want to block.
3. Select the radio button corresponding to what should be done to existing comments by blocked users(Leave as it is, unpublish, delete).
4. Choose the content type corresponding to which you want to block the user from commenting.

Documentation : http://drupal.org/node/1806418

Poem CAPTCHA is an unique kind of CAPTCHA which uses verses of poems displayed as an image with disturbing informations in the background to provide a challenge.

Installation:
Installation is like with all normal drupal modules:
extract the 'poem_captcha' folder from the tar ball to the
modules directory from your website (typically sites/all/modules)
or into the modules/captcha directory.
Further steps:
- Move the poems directory to a place inaccessible from the web.
- Enable the module
- Configure the module to use the poem dir's new place.
- Add more poems or fonts if necessary.

Dependencies:
The module depend on the basic CAPTCHA module, and need GD and
TrueType support.
No UTF-8 support with PHP's builtin font! If you want to use UTF-8
characters, you should use UTF-8 enabled ttf fonts!

Configuration:
The configuration page is at admin/config/people/captcha/poem_captcha
inside the main CAPTCHA module. You can tweak the poem CAPTCHA to your
liking there.

This project integrates with the OpenX ad server to provide an ad based CAPTCHA.

An input filter that expands a simple macro into an OpenX JavaScript tag for banners, campaigns or zones is included.