That's the six hundred million dollar question in my mind.
How exactly did Google know that those other institutions were under attack?
Unless the attack resulted in rooted Google machines that then attacked outward, or all those institutions were running on Google Apps.
Major institutions running on Google Apps seems unlikely (Are any major institutions outside of academia running Google Apps hosted by Google?). And attacking outward from a rooted box inside Google's network seems careless, unless the attackers were leveraging some dedicated pathways that made their job easier. Which suggests the breach was far more serious than indicated.
Google's security team eventually managed to gain access to a server that was used to control the hacked systems, and discovered that it was not the only company to be hit.
How exactly did Google know that those other institutions were under attack?
Unless the attack resulted in rooted Google machines that then attacked outward, or all those institutions were running on Google Apps.
Major institutions running on Google Apps seems unlikely (Are any major institutions outside of academia running Google Apps hosted by Google?). And attacking outward from a rooted box inside Google's network seems careless, unless the attackers were leveraging some dedicated pathways that made their job easier. Which suggests the breach was far more serious than indicated.