Many point to an episode in 2012, when Russian security researchers uncovered a state espionage tool, Flame, on Iranian computers. Flame, like the Stuxnet worm, is believed to have been produced at least in part by American intelligence agencies. It was created by exploiting a previously unknown flaw in Microsoft’s operating systems. Companies argue that others could have later taken advantage of this defect.Worried that such an episode undercuts confidence in its wares, Microsoft is now fully encrypting all its products, including Hotmail and Outlook.com, by the end of this year with 2,048-bit encryption, a stronger protection that would take a government far longer to crack. The software is protected by encryption both when it is in data centers and when data is being sent over the Internet, said Bradford L. Smith, the company’s general counsel.