Howdy, I'm Doug Davis, Director of the Computer Operations Department of the School of Engineering and Applied Science at Southern Methodist University. While my job is primarily administrative (the network and computer nerds work for me) my background is in the area of unix kernel/network development. We (meaning computer opertions) manage everything from little mac's all the way to supercomputers. There are varying degrees of security reqirement on each machine. Also this being a, "fundementally hostile enviornment", leads to more elaborate protection schemes. Since often times you can no more trust the users on a neighboring machine than the internet as a whole.