Mostly cracker open an application with Debuggers to study. But when an application is protected then debugger will display following message.
Lets take some example of a protected application and an unprotected Application
Protected Application:
Here you can see trial period command is invisible or encrypted.
Unprotected Application:
Here the trial period command become very easy to cheat.
Forms of Cracking:
key gens, patches, trial reseter and cracked exes are different forms of cracking.
If you are interested in cracking visit.
ap0x.jezgra.net
www.tuts4you.com
http://unkn0wn.ws/
http://hackhound.org/