MediaWiki Administrator's Handbook/Spam and Spammers
On wikimedia wikis, spamming is the addition of unwelcome commercial links and/or language, either added to already existing pages, or added as an entire page.
The various projects have vast differences in what is defined as spamming, and what to do about it.
SimpleCaptcha is the default captcha in ConfirmEdit. This captcha prompts user to solve a simple math question to prove that they are not spam bots:
SimpleCaptcha can be easily bypassed by simple script, so it is recommended to use more complex capchas.
FancyCaptcha is a traditional graphic captcha, that prompts user to type letters that appear in the picture:
To create captcha's images you will need to run a python script. But you will not need python on your web-server to use this captcha, you may create images on your desktop, for example, and just copy them to your wiki web-server.
MathCaptcha is another captcha mechanism for ConfirmEdit. To run it you will require TeX support within your MediaWiki.
Note that ConfirmEdit is quite sensitive to version mismatch. The last version of ConfirmEdit should work well with the last version of MediaWiki. If you want to use ConfirmEdit with a legacy version of MediaWiki, you might spend a lot of time looking for a matching version of ConfirmEdit in the SVN repository. Some version matches are mentioned on the extension home page but not all of them.
ReCAPTCHA is a captcha extension for Mediawiki. It offers strong visual and audio capchas.
MediaWiki's abuse filter extension can also be very useful in stopping spammers, in fact, it can outdo the other methods described above if configured properly while being less intrusive to the user. The main challenge is to determine how strict you want to be - you can be too strict but have virtually no spam - or you can be lenient and make do with some spam.
This site (en.wikibooks) mainly combats spam with the help of an abuse filter which blocks users with less than two posts from posting external links. This filter is particularly effective as spambots are focused on including external links and the abuse filter takes care of them, while the threshold is deliberately set low so that genuine users aren't affected.
If you use this method, expect false positives from time to time. You may wish to include a page where users can do that, in Wikibooks this page is used.
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