John the Ripper : A powerful, flexible, and fast multi-platform password hash
Cracker, THC Hydra : A Fast network authentication cracker which support many
different services, Aircrack : The fastest available WEP/WPA cracking tool, SolarWinds : A plethora of network discovery/monitoring/attack tools.
These techniques might be prevented if the detailed instructions is regulated on the Internet for free downloads; and it is not good at all for these detailed instructions to be available freely. Network administrator can learn a lot in terms of what the hacker community is up to by monitoring the hackers site.