New user registration linked to server ip address?

[bigrover]

We found a new user registration in the moderate users feature of the admincp that shows the ip address of the server itself next the the username and email address of the new user. We are trying to determine how the address of the server could wind up there. Where is that ip address being pulled from when the new user is signing up? Can it be spoofed during the signup? Does this indicate that either our site, or another site on the same ip address is corrupted and acting as a proxy or some other tool allowing spammers to hide themselves? I am looking for some guidance on how to resolve this issue, as in dealing with out hosting provider to change ip's, etc.

I have done a comparison of the code loaded on the site with the originals for the version we are running and they match.