BAD HARDWARE WEEK

The attackers also had access to an internal Google directory called Moma that stores information about each employee's work tasks, it said.
Seems that some important source code is stolen ! 
The intruders do not appear to have stolen passwords of Gmail users, and the company quickly started making significant changes to the security of its networks after the intrusions.
By clicking on a link and connecting to a “poisoned” Web site, the employee inadvertently permitted the intruders to gain access to his (or her) personal computer and then to the computers of a critical group of software developers at Google’s headquarters in Mountain View, Calif. Ultimately, the intruders were able to gain control of a software repository used by the development team.