Spam Prevention

A CAPTCHA is a challenge-response test most often placed within web forms to determine whether the user is human. The purpose of CAPTCHA is to block form submissions by spambots, which are automated scripts that post spam content everywhere they can. The CAPTCHA module provides this feature to virtually any user facing web form on a Drupal site.

Co-maintainer wanted

We do this our spare time, which is unfortunately almost nonexistent at the moment due to real life obligations. To give the CAPTCHA module the required level of maintenance, an extra co-maintainer would be welcome. If you're interested in helping with this very popular module, please contact me or open an issue in the CAPTCHA module issue tracker.

The Spam module provides numerous tools to auto-detect and deal with spam content that is posted to your site, without having to rely on third-party services.

The Spam module provides a trainable Bayesian filter, automatic learning of spammer URLs, flagging of content with an excessive number of links, the ability to create custom filters, and more.

[UPDATE: 1.2 was not correct as some of the hooks would not get defined. More or less, that means some of the functionality would not work properly. Please upgrade to 1.3 to fix the problem. See #1222546: The List of Spam Comments is Broken and #1298480: "Mark as Spam" and "Mark as Not Spam" links for comments going to 404 page. among other similar bug reports.]

Bad Behavior is a set of PHP scripts which prevents spambots from accessing your site by analyzing their actual HTTP requests and comparing them to profiles from known spambots. It goes far beyond User-Agent and Referer, however.

Invisimail provides a content filter to hide email addresses from spam-bots. Email addresses are converted to ascii code and optionally written to the page using a concatenated JavaScript "write" command. The email addresses will appear on the page normally, but their html source will be obscured so as not to appear as an email address to email harvesting robots. Invisimail also provides an option to automatically create mailto links for email addresses.

Features

The AdminRSS module creates RSS feeds for the administrative information for Drupal websites.

These feeds are protected with a keystring that must be set in admin/settings/adminrss page, and should accordingly be safe enough and updated often. The resulting pages can then be read at:

The SpamSpan module obfuscates email addresses to help prevent spambots from collecting them. It implements the technique at the SpamSpan website (a German version is also available). The problem with most email address obfuscators is that they rely upon JavaScript being enabled on the client side. This makes the technique inaccessible to people with screen readers.

Sept 5, 2008 Update: this module is unsupported.

Similar modules include Antispam (which includes Akismet protection), Mollom or Spam.

This module allows you to use the Akismet web service to protect your site from being spammed. Originally implemented by markus_petrux.

This module allows users to flag nodes and comments as offensive for the adminstrator to review.

This module is in the rearchitecting period. All changes will happen in 2.x branch.

The admin can specify which type of nodes are allowed to be flagged.

Implements Project Honey Pot's http:BL service for Drupal. http:BL can prevent email address harvesters and comment spammers from visiting your site by using a centralized DNS blacklist. It requires a free Project Honey Pot membership. This module provides efficient blacklist lookups and blocks malicious visitors effectively.

http:BL has been adopted for use to enhance protection on Drupal.org.

Overview

Captcha Riddler is a sub module of Captcha that lets site administrators create their own questions to foil automated spam bots.