The researchers found that when connected to a target user on a Skype call, they could record the audio of the user’s keystrokes. With a small amount of knowledge about the victim’s typing style and the keyboard he’s using, the researchers could accurately get 91.7 percent of keystrokes. The attack does not require any malware on the victim’s machine and simply takes advantage of the way that VoIP software acquires acoustic emanations from the machine it’s on.

Source: Recording Keystroke Sounds Over Skype to Steal User Data | On the Wire