Keep track of IP of registered members?

I’m wondering if it is possible for WP to keep track of the IP address of registered members. WP does this when people make a comment, but not when they register. It is very important for my particular WP install because I allow everyone to post upon registration, and if people violate the TOS, I want to ban their IP, not simply delete their account which all they’ll have to do is create a new one (it’s for a web marketplace / https://www.webunload.com). Any help?