Sorry guys, but I don’t think there is a solution with current squid version.
Maybe you can try to switch to NS 7 and block/unblock skype using DPI.
And, even if we find a solution working today, a future skype version could stop to work again.
It’s hard to deal with proprietary protocols.
But what are with the rest like Windows Update or to bypass single systems etc. would be great to have that solution
Is it possible to install a Socks5 proxy instance inside our nethserver? That would be a workaround for this problem. Any experience with this?
I honestly don’t know anything about Socks 5 proxies.
If you find a simple proxy which works with CentOS 7, I think I can help you to set it up.