Mit Squid scheint es relative easy zu sein skype aus dem Netz zu bekommen. Mal schauen.
-- snip --
# Prevent Skype connecting HTTPs using CONNECT requests to IP addresses (those not using domain names)
acl numeric_IPs url_regex ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+
http_access deny CONNECT numeric_IPs all
# Prevent Skype connecting http
acl Skype_UA browser Skype
http_access deny Skype_UA
# Prevent anyone to download anything from skype website
acl Skype_domain dstdomain skype.com
http_access deny Skype_domain
-- snip --