Skype is blocked by default after installation of Websense Express.
In the Websense Master Database, Skype is assigned to the protocol category called P2P File Sharing. This category is blocked by the policy Basic Security, which is set by default after Websense Express is installed. So check in your Master Database under P2P File Sharing and ensure that it is blocked.
The initial problem of detecting Skype is in itself a rather difficult one. Skype, is it right for you? has description and paper references to the problem.
Final notes from that link (which is a good read).
So, the final questions, is Skype Spyware?
In my opinion No. It does not contain spyware and never has.
Is Skype useful?
In my opinion Yes.
Is Skype beneficial to my environment?
Is it? That’s a determination that only you can make.
Do your clients sit behind NAT, Firewalls, and/or proxies?
Then they won’t be supernodes or Relay nodes. They are just clients.
Do you have a requirement to monitor all IM, file transfers, and/or voice calls? If so, Skype is hard. It’s encrypted.
Once you figure out Skype is active, intercepting the traffic is a much more complicated problem.
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
Best Answer
Skype is blocked by default after installation of Websense Express.
In the Websense Master Database, Skype is assigned to the protocol category called P2P File Sharing. This category is blocked by the policy Basic Security, which is set by default after Websense Express is installed. So check in your Master Database under P2P File Sharing and ensure that it is blocked.