CoDeX-W0rm - what happened here?

One of my stupid Windows servers has been hacked, and was running Serv-U
FTP with a login message of "This Pubstro Hacked By Mediax!"

I found what Pubstro's are, but when searching through the files in the
Serv-U folder, I found this in the install.log

CoDeX-W0rm has infiltrated the system succesfully!

I did a search on Yahoo and SecurityFocus, and could not find any results
for this.

Does anyone have any idea what this worm is, or with the info I've given
you, how they got into my system. This happened around Dec 27th 2003, and
I just found it :-(

Thanks,
Chuck Rock
Received on Feb 03 2004