i want to blocj skype in my network i couldnt do it from kerio firewall because it is impossible can some one here explain me how one can do it through GPO ?PLEASE EXPLAIN THE PROCEDURE STEP BY STEP OR GIVE ME A LINK FOR IT
THANKS IN ADVANCE
Did some post and ways to block it (skype) :)
But still not complete one :( .. trying the best :)
1) Block IP Addresses to Skype Authentication Servers
Block 126.96.36.199 & 188.8.131.52. This won't affect people who have already signed up and saved their Skype credentials on their PC. It only works for new users that try to authenticate for the first time. So for new users that first install Skype, it should prevent them from authenticating and thus, they won't be able to get in. I have not verified this "tip" still works today. It updates all the time and have many new features .. . To test uninstall Skype (to similate a fresh install), block the IPs, then reinstall Skype.
2) Block Skype using ISA Server 2006
If you use ISA Server 2006 proxy server you can block various IM software clients including AOL Instant Messenger, MSN Instant Messenger, Yahoo Instant Messenger, and ICQ. It might also work with Skype as well, but Skype can be tricky to block. Although this awesome ISA Server 2006 article titled "Getting started with Microsoft ISA Server 2006, Part V: Configure HTTP Filter" seems to indicate using ISA Server 2006 to block Skype can be difficult. But it's a great resource for blocking other IM clients and even .torrent files.
3) Block Skype using Group Policy (corporate environments)
Go to Computer Configuration / Windows Settings / Security Settings - Software Restriction Policies - Additional rules. Then create rules for the hash of the specified .exe to block no matter where it launches from. Problem with this is that Skype updates regularly, so you'd have to keep on it. So alternatively, block a specified directory, i.e. \program files\skype and disallow anything from launching from within that directory.
And the way that need to pay ...
Alternative methods for blocking Skype
1)NetSpective from Verso Technologies - Can be configured to block over 20 P2P and Instant Messaging programs, including Skype. NetSpective is available in enterprise and carrier versions. Verso has supplied China Telecom with their carrier class of NetSpective.
2)Packeteer's PacketShaper - detects Skype and other P2P traffic and allows the administrator to apply Quality of Service regulations or block it completely.
3)SonicWall's Unified Threat Management appliances - SonicWall has a PDF presentation on how to block Skype with their hardware, or you can read the HTML version in the Google cache or on the web site .
4)Fortigate from Fortinet - capable of blocking Skype and other P2P applications.
5)Check Point's InterSpect - Using InterSpect with Check Point's SmartDefense system can identify and block P2P applications including Skype.
6)Cisco equipment running IOS version 12.4 (4) T - This is the "free" option, providing that your network already uses a Cisco product with this IOS version. See Cisco Tips & Tricks for the instructions on there site and fenitooo skype:))) .
7) Blocking Skype Using Squid system
8) Blocking Skype Using OpenBSD software.
P.S. Its not he end of the war with skype ....
The last thing is to write the hash rule and he can block it very well :)
Good luck ,
Source: block skype from GPO?HOW TO DO IT?