The author of Age of Empires categorizes the many ways in which multiplayer games can be compromised, and suggests strategies for mitigating the risks from hacking.
I've lost count of the number of developers I've encountered who thought that because something they designed was complicated and nobody else had the documentation, it was secure from prying eyes and hands. This is not true, as I learned the hard way. If you are skeptical, I invite you to look at the custom graphics file format used in Age of Empires. Last year, I received a demanding e-mail from a kid who wanted the file format for a utility he was writing. I told him to go away. Three days later he sent me the file format documentation that he reverse-engineered, and asked if he missed anything. He hadn't. Thus, this is a perfect example of rule number five. Yes, I've borrowed it from cryptography, but it applies equally well here.
(via Camworld)
