Hey everyone,
two weeks ago the management decided to block Live Messenger in our company. I’ve been given the task to get it done. Here’s the problem.
I’m using a ISA 2006 firewall; and we decided to start using Opendns as well. I followed Microsoft’s advice on blocking Live Messenger; blocking traffic signatures – because apparently, Live Messenger will just use any open ports anyway these days.
Along that, we used Opendns and set it so that messenging domain names are blocked (amongst others). This takes care of blocking domain names that Live Messenger uses to contact it’s services.
That’s as far as the theory goes. For about two weeks everything went fine. No-one could use Live messenger (or MSN Messenger, before you should ask). But for the last two days, Live Messenger can be used without a problem – which isn’t what we wanted.
What am I missing here? I don’t see why the rules that we used 2 weeks ago, would suddenly stop working. Are there other methods I could use to make sure that Live Messenger traffic is blocked?
Before you ask, disabling Live / MSN Messenger on the desktops isn’t an option. Web Messenger has to be blocked as well (hence Opendns), and some of the machines I “manage” aren’t a member of the domain (being used by students which we decided not to give an user account for various reasons).
What to do, what to do?