Is there a way to block Skype using Squid?
Blocking Skyep in squid is a two stage process, firstly Skype by default uses an outbound connction on a port in the range of 2940-3000, so these should be blocked on your egress filtering.
However, if skype cannot connect on these ports, it will try to connect using port 443, which you obviously cannot block without preventing SSL access to any sites. However, Skype uses a connect method called 'Connect' to make this connection, so this can be blocked by creating an access list that looks for connections to an IP address, using the 'Connect' method:
# Your acl definitions acl numeric_IPs urlpath_regex ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+ acl connect method CONNECT # Apply your acls http_access deny connect numeric_IPs all
Take a look at this article for more information.
You may want to read network-admin-guide-version2.2.pdf for relevant information. There's also a document which details how Skype gets around firewall and proxy restrictions but I don't have the URL for it.
File you say can be found here: http://download.skype.com/share/security/network-admin-guide-version2.2.pdf this maybe can help as you say...