I just had someone partially explain this to me. From what I understand is that a "Spoof" attack is when someone out in "networkland" tries to steal a machines IP and/or Hardware address. I would think they do this so that they can perform illegal activities/hacking from a port that is not their own, hence making it mor difficult to track.
Do you have your wireless connection password protected?
iMac 800 mhz, 768 MB RAM, 60 GB HD,
Titanium Powerbook 800 mhz, 1 gig RAM,
30 GB HD, ATI Radeon 8500
Dimension 8300 2.66 ghz, 1256 MB RAM, 120 GB HD, 64 MB Gforce4