Question

How to block skype ports

Asked by: alexfinbow

I am trying to restrict a networks access to using Skype.  I know that skype uses 80/443 to initiate the connections between parties, and then assigns a random UDP port for the transfer of the data.  I know that i could create firewall rules to detect skype traffic, but all i have to work with is a 3com managed switch, which can either allow or block ports.

Any suggestions? (other than putting a small server in with the switch, which at present isnt an option)

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Asked On
2008-07-29 at 01:29:11ID23603239
Tags

Skype

,

Blocking skype ports

Topics

Chat / IM Software

,

Network Switches & Hubs

,

Networking Hardware Firewalls

Participating Experts
1
Points
125
Comments
8

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Answers

 

by: dibbzPosted on 2008-07-29 at 01:41:19ID: 22109611

The only way I found was to block all numeric addresses in squid or your choice of web filtering app.

Squid example;

# 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 numerics_IPs all



 

by: alexfinbowPosted on 2008-07-29 at 01:44:34ID: 22109633

i have no servers with which to run any sort of apps or i'd be golden, damn and blast skype!

 

by: dibbzPosted on 2008-07-30 at 00:01:20ID: 22118017

Skype is designed to be difficult to block, you could use group policy to stop people running it.

From another EE posting: (http://www.experts-exchange.com/Microsoft/Windows_Security/Microsoft_ISA/Q_23240758.html)

kanashii23:
Note this is cut from another thread in Experts Exchange.
So i dont intend to claim point for this.

farhankazi:
I would use Restriction Policies in Windows Server 2003 create 'Hash rule'.

For more info:
http://support.microsoft.com/kb/324036
http://www.windowsnetworking.com/articles_tutorials/Software-Restriction-Policies.html

SheharyaarSaahil:
How to block skype
http://blog.tmcnet.com/blog/tom-keating/skype/block-skype.asp
             
spyder357:
Three ways you can go about doing this....

1) Is setting up a group policy to restrict the install of this software outright.

2)Setup a group policy to set permissions on the skype service.  Set the permissions to only give the IT department the ability to run it.  That way when they reboot their computers after getting the new policy the service will fail to start.
(This is my favorite...no one will be able to figure out why its not working :)   )

a.  First you must install skype on the computer that your creating the policy from (do it from your desktop).
b.  Go under /Computer Config/Windwos Settings/Security Settings/System Services and you should see the Skype service, select it and place the "appropriate" permissions on it.

Any computer with skype installed will be affected, any computer without it will disregard the policy.

3.  Block the skype ports on the firewall. This involves setting outbound ACL's on your Cisco...refer to Cisco's documentation for your IOS version on how to do this.

Do option 2...it will be funny I promise :)

 

by: alexfinbowPosted on 2008-07-30 at 00:38:34ID: 22118170

this is for managed offices, which means i have no control on what is installed on peoples machines, nor do i have access to any servers with which to use GPO's.   All i've done is enable 40 odd ports and restricted every other port, hopefully that might do the trick!

 

by: dibbzPosted on 2008-07-31 at 01:59:01ID: 22127956

I only had 80 and 443 open on squid and it gets around that no worries, it's designed to get around as many obsticles it can.. good luck!

 

by: alexfinbowPosted on 2008-07-31 at 08:44:34ID: 22130776

oh dear, thats not good! :( ill see what happens though i might try and make a call with it

20120131-EE-VQP-002

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