Security vulnerabilities in Windows and Internet Explorer were said to be among the ways the hackers accessed personal accounts and confidential data from Google's servers.
The internet search firm started phasing out Windows in January, according to the Financial Times, citing Google employees.
The move to other operating systems could effectively end the use of Windows at Google, which employs more than 10 000 workers internationally, said the FT.
New employees are not being offered Windows and employees wanting to stay on Windows need clearance from "quite senior levels", according to Google employees.
But security concerns merely accelerated Google's policy of running the company on its own products, such as the Chrome web browser and the coming Chrome operating system, employees said.
Google's Chrome OS will compete with Windows, which is found on more than 80% of the world's computers, according to research firm Net Applications.
Because of its market dominance, Windows has been more concertedly and consistently been targeted by attackers, earning a reputation for being more vulnerable than other operating systems.
But Microsoft says its Trustworthy Computing program is paying off and the latest versions of Windows and Internet Explorer developed using its Security Development Lifecycle (SDL) are so secure that attackers are now focusing on more vulnerable third-party applications and browser plug-ins.
The fact that the number of vulnerabilities fixed in Windows Vista in the first year was roughly half the number for Windows XP, a third of the number for Mac OS X 10.4 and a fifth of the number for Ubuntu Linux, proves the SDL is working, said Steve Lipner, senior director of security engineering strategy at Microsoft.
This article was orginially published by Computer Weekly