Net send is possible over the internet if proper ports are opened and such.
but...
"That would Own!"

first, I hate the phrase of "Owning" or worse pwning.
You got scanned. big deal. make a note of the IP, and if youve done your security right, AND you pay attention, you will be fine. retaliation only causes more traffic on a already busy internet. Plus its prolly just a damn script. if they are hammering you with scans, etc get the ISP using Whois. (thats all Ill tell you, time to learn how.)
then use the whois info to get ahold of [email protected]