Portscanning is legal in some parts of the world and not legal in other parts, it depends on where you are...
Yes it can be detected.
Take good advice mate.. don't scan other peoples systems...
Maybe learning things 5-10 years ago was easier because admins were more lenient.. nowadays most people take things pretty personally..
However there is no excuse to scan other systems to 'learn' anymore... hardware is *way* cheaper, you have VM systems like VirtualPC, VMWare, UML etc.. and tons of resources... and with the current security bubble thats going around, more than enough attention focused on it to make it easy to learn.
Cheers,
