[Wlug] Who is port scanning me?

Hi everyone, I'm constantly getting port scanned from a certain IP address on our internal corporate network. I'd really like to find out where and who this person is, but don't know much outside of ping, traceroute, nslookup, etc .... I was wondering if anyone knows of any tools that can get me more information on this person? This happens to be on our private network, so most internet tools I don't think will help much. Thanks for your time. Matthew