Extension:Bad Behavior

Bad Behavior is a set of PHP scripts which automatically blocks harvesters, spam bots, and other funky stuff. Bad Behavior version 2 was released on July 4, 2006 with better support for blocking malicious edits on MediaWiki. It installs much as any other extension.

By default, it adds a cookie which can be disabled with appropriate configuration.

It has some problems if you are using cache, in particular: 1) serving of cached wiki pages can't be blocked, only form submission will; 2) IP of last reader of a page can be shown to the next.

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Bad Behavior on MediaWiki