Manual:$wgProxyList

Details
Big list of banned IP addresses.

Example:

Example
Copy and paste a comma-delimited list (e.g. 1.0.170.183,1.0.170.188,1.0.170.234,1.0.170.24) of open proxies into MediaWiki:Openproxylist; then put the following in LocalSettings.php:

Comments

 * A comma-separated list of known 'bot IP's is available from http://www.stopforumspam.com/downloads