port scan issues

I’m running w2k sbs w exchange running.

My app log gets full every 2 hrs because of port scans. I know port scans are not unusual but this is too much.
Anything at all I can do? ISA doesn’t even report what IP address its coming from.

Exchange is also sending THOUSANDS of spam emails. I’ve checked with several antivirus and spyware removers and non of them have reported anything