User IP

Is it possible to retrieve a users login IP to trace it?
We think we have an unwanted person on our site who has created an account using bogus info but can only confirm it by checking the IP.
Would it be hard to create a page to be used by admins to list user name and IP.
A log of data retrived whenever page is opened showing this info for say the last 10, 20 or 30 days.
I would be happy if even I was the only one to use such a tool if it could be created.
Thanks
We think we have an unwanted person on our site who has created an account using bogus info but can only confirm it by checking the IP.
Would it be hard to create a page to be used by admins to list user name and IP.
A log of data retrived whenever page is opened showing this info for say the last 10, 20 or 30 days.
I would be happy if even I was the only one to use such a tool if it could be created.
Thanks