Having been bothered by some unsavoury spam attacks on my weblog comments, I have now installed MT-Blacklist .

Following are the instructions I followed:
First, download, unpack the archive and upload to your webserver in ASCII mode. Put the files in the following locations relative to your main Movable Type directory (abbreviated MT_DIR below) where mt.cgi resides.

MT_DIR/mt-blacklist.cgi <--- Should be in the same directory as mt.cgi
MT_DIR/plugins/Blacklist.pl
MT_DIR/extlib/jayallen/Blacklist.pm
MT_DIR/extlib/jayallen/MTBlPing.pm
MT_DIR/extlib/jayallen/MTBlPost.pm

Set the permissions for all files to 755 (-rwxr-xr-x).

go to http://YOURDOMAIN/MT_PATH/mt-blacklist.cgi

-then configuration can be completed.

There is a master blacklist here that can be used to fill your own blacklist.

I have come across here a routine to update this without a cron job.

New spam identities can be shared with the master blacklist. A great way to work together to beat this scourge.

To run MT-blacklist: www.mydomain.com/mt-cgi/mt-blacklist.cgi