I have first hand experience with all kinds of software security related, from a black hat prespective in malware related software and white hat perspective in professional penetration testing software.
I used to install trojans and all types of malware in others computers mostly just for fun and in some cases just to get to know the softeware in it self.
Using a well knowed trojan (reverse conection), configurating the server with no-ip address, so that it will be dynamic, cypher the .exe, use a pdf exploit for spoorf the extension, install keylogger or stealer, install blackhole exploit kit. Etc etc etc
Once when i was in higschool, using ophcrack i cracked the Administrator password. It was Wind0ws
Later a friend confirmed using a sociel engenering atack.
I installed in the library computers CS 1.6 and a roge version of MSN chat.
This version would send the logins to me via email.
I also installed a fake page bookmark and cracked all the wifi's around, to change the SSID to some funny mensage.
Those are just some funny experiences I had back in the days.