The patch is working quite nice­ly for me - in 12 weeks, only one spam­mer got through (and ended very quick­ly on my black­list). So I extrac­ted my code into a se­pa­ra­te mo­du­le, re­du­cing the size of the patch for the ori­gi­nal mul­ti­ping mo­du­le.
You can get it on my Dru­pal page. Don't for­get: It is not en­ough to in­stall the mo­du­le, you have to apply the patch in­clu­ded to the ori­gi­nal track­back mo­du­le.