Fred Chang has a theory about how hackers affiliated with the Chinese government hacked into Google and at least two dozen other major American companies. Chang is a professor of computer science at the University of Texas — so we should listen to him. But he is also the former director of research for the National Security Agency, so he has a pretty good idea of what hackers can do — and whether these things can be picked up by the government or industry.
Chang says he has no inside or special knowledge, but here is his theory: the hack was much more of a sophisticated intelligence operation than many believed. The first step was espionage and data collection.
The second step was the hack itself. Chang believes that the Chinese hackers figured out the identities of the system administrators for various computer networks. Then, the hackers figured out, using publicly availably Facebook data, the social networks that these systems administrators were part of.