Extension:Bad Behavior

The Bad Behavior extension automatically blocks harvesters, spam bots, and other funky stuff.

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