Blocking Skype is difficult unless you block all ports by default and only open the ones you need for other applications. Skype is very persistant in trying to find an available port to use.
Yes, I know it is difficult to block skype I have created a software restriction policies to hash to the executable, in the political domain, but only blocks a certain version, create a new rule for each version of Skype. However I would also block messenger and hotmail, can someone tell me how to do it with Wingate? thanks