If you ever wanted to know what Google does to maintain its high level of security, here’s your chance. Google Infrastructure Security Design Overview provides quite a bit of information on the subject.
This document gives an overview of how security is designed into Google’s technical infrastructure. This global scale infrastructure is designed to provide security through the entire information processing lifecycle at Google. This infrastructure provides secure deployment of services, secure storage of data with end user privacy safeguards, secure communications between services, secure and private communication with customers over the internet, and safe operation by administrators.