they all have a law prohibiting the unauthorized use of computers. This includes the use of any system you have not been permitted to use.
That's true, but what's authorized or not may be subject to interpretation.
Your computer is already connected to others by virtue of being in the net.
Some communications with remote systems are assumed to be always authorized,
like issuing HTTP requests to a remote system. Admins and owners of various
servers may have different interpretations of what they consider an acceptable
communication.

If they are running a web server only, would they be offended if you said
ftp <host> thinking that they might also have an ftp server? How about
telnet? Would they interpret this as a "port scan" or an unauthorized attempt
to "probe" their system? Every attempt to communicate is subject to
interpretation.

By being connected, you can be assumed to have granted others the right
to talk to your system by way of ping, or other means of inquiry. Where
do you draw the line between normal talk between hosts and unwelcome
probing?

Cracking is like the old saying about obscenity. It's hard to define,
but
I know it when I see it
http://216.239.37.104/search?q=cache...hl=en&ie=UTF-8