Though it's been 2500 years since Sun Tzu wrote "The Art of War", many of his lessons remain relevant. His teaching contains several passages that seem especially suitable for people who work in Information Security:
* "Those who disable foreign armies without combat are the best teachers of the Art of War."
* "Before you fight, first learn the skills of the enemy's workers, and then fight them according to their weaknesses."
* "When you can perceive subtlety, winning is easy."
Without a doubt, this information is key in preparing for attempted security breaches. Without it, determining what to attack and how to do it is impossible. Search engines have become important tools for collecting data and other intelligence. However, despite Google hacking's many years of use, its techniques have perhaps not always been well-treated or publically shared.
There is also a pretty good book from a spanish Microsoft MVP (yeah it sounds bad but still its an important award, :\)
http://www.informatica64.com/libros.aspx?id=hackingBuscadore...
It's a shame they decided not to translate it, anyone is up to it here? It contains everything that you'd ever wonder and much more.