Block Team Viewer

Hello,
I need to completely block team access from outside to internal clients. I need to make sure in my network that no on uses team viewer in my network

I have following design

Internet>>Router>>ASA>>Inside

I would highly appreciate any help.

Thahnks
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cciedreamerAsked:
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MarcusSjogrenConnect With a Mentor Commented:
The biggest advantage of using TeamViewer is that they are not blocked by firewalls and routers. You would probably need a layer 7 filter to be sure about filtering it, like Websense or Fortigate.

TeamViewer isn't just using dns to resolve its routers/servers but also bare IP-addresses. Hence the need for filtering equipment.
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MrC63Commented:
What brand of router is it, and what's the ASA device?  Is it a Cisco ASA?
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cciedreamerAuthor Commented:
I have Cisco Router 1840 and Cisco ASA 5540.


Thanks for the help.
Samir
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MrC63Commented:
Thanks, that helps.  

Next I want to clarify something.  You say you don't want anyone to use TeamViewer in your network.  Does this mean you want to block all TeamViewer activity even if it was between two computers inside your network, or is your concern Teamviewer access from computers outside your network (but between computers inside the network it would be fine), or is it all of the above?
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cciedreamerAuthor Commented:
I appreciate your help.
I want block outside my network and allow for certain pc's that I want to allow and block other computers.

Thanks
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TMekeelCommented:
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cciedreamerAuthor Commented:
Sorry I just forgot to mention that my internal clients are using TMG Proxy to connect to internet. Thus team viewer grant to access to outside going through proxy.
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MrC63Commented:
This is a bit of a confusing configuration.  You have both a router and a firewall (both almost the same) and now a third proxy?  

Which system (or systems) is TeamViewer currently able to access?  I'm afraid I can't give you much more advice until I know where TeamViewer is gaining access to your internal network.
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cciedreamerAuthor Commented:
I am allowing my internal users to access internet using our proxy server instead of going direcly through ASA.
My TMG firewall is behind Cisco ASA.
I want to make sure in my internal network on one uses team viewer except for them I allowed.
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MrC63Commented:
How does your proxy server access the Internet?  Does it go through the ASA (and then subsequently through the router) ?
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cciedreamerAuthor Commented:
Yes. It goes through the ASA and then router
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MrC63Commented:
This is an exceptionally unusual configuration. Is there a specific reason why you go through a proxy, then a firewall and then a router.

Since you have an ASA firewall, why not use it as the point of entry / exit and eliminate the others.  This would allow you to manage both inbound and outbound traffic from a single source, rather than trying to use different devices / programs to control access.

Maybe there is something else you haven't described that justifies the three layers?  If you need to use all three, and if you need to allow access to certain PC's, this becomes exponentially more complex.
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pgm554Commented:
Why not set up a GPO that forbids them from installing 3rd party software without admin permissions?

Just go into AD and change their user rights.
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cciedreamerAuthor Commented:
Is there any to block them through TMG ? since my internal users are proxy in there browsers
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MarcusSjogrenCommented:
Just found out that Cisco actually have a module called CSC which can be installed in the ASA and its a content filter which can filter for example remote software.
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cciedreamerAuthor Commented:
That's the right clue ! I blocked them through Websense
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