In January, Google disclosed that there had been a major, successful, cyber attack against Google. It should be noted that other prominent US companies also reported successful major security breaches as well. At the time, the extent of the attack was largely unknown to the public. The NY Times reported (Published: April 19, 2010, Cyberattack on Google Said to Hit Password System) that someone close to the investigation stated that the attack hit Google's most sacred system--the password system. This system, code-named Gaia, controls the passwords to millions of Web services, including e-mail and business applications. Gaia allows users to use a single sign-in function to access a broad range of tools (without re-entering their password).
One of the concerns that outside experts have warned against is that the attackers may have discovered weaknesses in Google's systems that perhaps Google may not even suspect. If so, the attackers could use the exploits to gain re-entry, steal data or corrupt the system.
(Source: https://www.nytimes.com/2010/04/20/technology/20google.html, or print: page A1 of the New York edition.)