Please be advised that (at least in WP 2.0.3, but probably older versions too), the option “Blacklist comments from open and insecure proxies.” (‘Options’ -> ‘Discussion’) doesn’t work any more, as the RBL which is being tested, has ceased to exist: https://lists.blitzed.org/pipermail/opm-announce/2006q2.txt
To switch to another (working) RBL, do this:
– edit wp-includes/functions-post.php
– find the text: opm.blitzed.org
– replace with: sbl-xbl.spamhaus.org
(do not touch the dots before and after the text)