United States federal laws explicitly criminalize port scanning. a much more frequent
occurrence is that the target network will notice a scan and send a complaint to the network
service provider where the scan initiated (your ISP). Most network administrators do not
seem to care or notice the many scans bouncing off their networks daily, but a few complain.
the scan source ISP may track down the user corresponding to the reported IP
address and time, then chide the user or even kick him off the service. port scanning
without authorization is sometimes against the provider's acceptable use policy (AUP).
network probing or port scanning tools are only permitted when used in conjunction
with a residential home network, or if explicitly authorized by the destination host
and/or network. Unauthorized port scanning, for any reason, is strictly prohibited.