Ballmer, Microsoft CEO from 2000 to 2014, said that while Amazon is a direct competitor to Azure, it's Google that could challenge Microsoft's Office 365 product. "With Amazon Web Services, Azure is the challenger, it has only one way to go, which is up. With Office 365 there is more upside than downside, and that's a Google risk," Ballmer said. Microsoft's cloud division has been growing fairly strongly, and it's an area current CEO Satya Nadella has flagged as the company's future. Microsoft's cloud business brought in $6.86 billion in revenue during the fiscal second quarter.