How to listen to Skype?

a Trojan on the computer of the victim listening to the audio.
no options.

Listen — unlikely, but to get parallel access to the correspondence, having the login and password is likely.
Tip: to change the password on the mailbox and then on Skype, and they should be different.
To watch.

officially — no way. this is one reason that the government does not like Skype, in many countries operators are required to provide wiretapping to combat terrorism and extremism, so Skype ban.
and actually who knows...

Hmm. To connect between a computer and a microphone, or use rendering software recording audio on the computer. Remotely listen — unreal.

In theory it is possible, recently opened their Protocol, but you will be rested in cryptography, which there more than anywhere else. Actually currently "listening to" Skype exclusively some special. service.