Microsoft has turned over Skype conversation contents to the U.S. government since at least February 6, 2011. Skype has long claimed to be “end-to-end encrypted”, an architectural category that suggests conversations over the service would be difficult or impossible to eavesdrop upon, even given control of users’ Internet connections. A 2005 independent security review admits a caveat to this protection: “defeat of the security mechanisms at the Skype Central Server” could facilitate a “man-in-the-middle attack””]
Source: https://gizmodo.com/why-doesnt-skype-protect-you-against-eavesdropping-835286370