TechCrunch reports that Ballmer made a few rather uncomplimentary comments about rivals to Microsoft's Windows Phone in an interview with LinkedIn founder Reid Hoffman last night.
When asked about Google's Android, he said that it was "uncontrolled" and vulnerable to malware.
Shifting to Apple's iOS operating system that runs on iPhones and iPads, Ballmer said that it was "high-priced" and "highly controlled".
Despite the recent glitzy launch of Windows Phone 8, Microsoft lags far behind Google's dominant Android and Apple's popular iOS in the global mobile software market.
It seems apparent that Ballmer views Windows Phone as a middle ground between the "wild" Android and "controlled" iOS.
However, the company still has a lot of work to do even to overtake third-placed BlackBerry. Canadian firm Research In Motion, maker of BlackBerry, has struggled of late but it has high hopes for the launch of BlackBerry 10 next year.
Also in the interview, Ballmer said that he anticipates other manufacturers making the "lion's share" of Windows PCs, tablets and phones, despite Microsoft getting into the market this autumn with its Surface tablets.
But according to All Things D, he added: "With that said, it is absolutely clear there is an innovation opportunity on the seam (of the intersection) between software and hardware… that is a seam that must not go unexploited by Microsoft."
Possibly tellingly, Ballmer also said that the company can still do more in the "under five inches" category, adding more fuel to speculation that a Surface phone could be on the way.