There’s a new Trojan horse computer virus that may affect Skype users. Although there aren’t any widespread cases of this Trojan actually impacting Skype users. According to Symantec Security Response:
Trojan.Peskspy listens in the data traveling between the Skype process and the audio device, it gathers the audio independently of any application-specific protocols or encryption applied by Skype when it passes voice data at the network level. Essentially, it sits below these security measures, recording the audio at the Windows level—before outbound audio from the microphone gets to Skype and after incoming audio leaves Skype and reaches the speakers.
Finally, the Trojan contains a back door, which enables an attacker to have the stolen audio conversations sent to a predetermined location, where they can later be listened to.
Naturally the Symantec recommeneded solution is to keep your virus definitions up-to-date.