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On bylaugh.org I simply renamed the weblog-tb.php file to something random and blocked the IP range - it stops all trackbacks and shows a 404 error.
edit-
He's just been on again and this is the result:
le="color: #000000"><?php Host: 85.255.113.158 /modules/weblog/weblog-tb.php/7 Http Code: 403 Date: Apr 07 11:25:56 Http Version: HTTP/1.1 Size in Bytes: - Referer: - Agent: Movable Type | | | /modules/weblog/weblog-tb.php/3 Http Code: 403 Date: Apr 07 11:26:59 Http Version: HTTP/1.1 Size in Bytes: - Referer: - Agent: Movable Type | | | /modules/weblog/weblog-tb.php/2 Http Code: 403 Date: Apr 07 12:52:50 Http Version: HTTP/1.1 Size in Bytes: - Referer: - Agent: Movable Type | | | /modules/weblog/weblog-tb.php/8 Http Code: 403 Date: Apr 07 13:08:48 Http Version: HTTP/1.1 Size in Bytes: - Referer: - Agent: Movable Type | | | /modules/weblog/weblog-tb.php/5 Http Code: 403 Date: Apr 07 13:33:27 Http Version: HTTP/1.1 Size in Bytes: - Referer: - Agent: Movable Type
Lot's of 403's until he tries another IP and then lots of 404's.