“An infected machine will use the software that handles audio processing within a computer and save the call data as an MP3. The file is then sent over the Internet to a predefined server where the attacker can listen to the recorded conversations.”
It is also possible that this trojan can affect other popular VoIP applications, although this isn’t proven.
The Trojan is named Trojan.Peskyspy. So to all you Skype users do some reading and research on how to protect yourself. Here are some articles that you all can browse through.
Trojan.Peskspy | Symantec
Trojan.Peskspy Blog by a Symantec Employee
And here is an interesting story about how Trojan.Peskspy attacks Skype encryption though Windows API.