Hey Mike,

Try this on your ISA:

It's possible to block Google Talk by :
==> URL blacklists :
a.. talk.google.com:443
b.. talk.google.com:5222
c.. desktop.google.com/download/googletalk/google-talk-versioncheck.txt?
==> By signatures (For more information, see HTTP Filtering in ISA Server
2004 )
2 User Agents :

a.. Google Talk
b.. Mozilla/4.0 (compatible; Win32)
==> By The Firewall Client Setting Dialog Box:

Add new application entry setting Or process name "GoogleTalk.exe", use the
"disable" key and Select the value 1 from the value list to block the
application


On 6/15/06, Mike Powell wrote:
> Does anyone have any ideas for blocking Google's new Google Talk client
> without blocking the Google web site? The IP addresses that the Talk
> client uses are the same addresses that resolve for Google. Even more
> difficult, Google doesn't have reverse (PTR) records to be able to
> usefully filter traffic to raw IP addresses. Even if they did, since the
> addresses are the same as for Google's web traffic (see above), blocking
> addresses used by the Talk client would break access to the Google
> website.
>
> Also, even though the documentation on the Google Talk web site states
> that the Google Talk client uses port 5222 (which we are successfully
> blocking), it seems to work just fine even if port 5222 is blocked and
> the only access is port 443(SSL). I know that it is working this way
> because I have tracked this in the logs, and it tries to connect on
> 5222, but also makes connections on 443 and then just keeps on going
> like there was no problem at all.
>
> We filter our internet-bound traffic through Microsoft's ISA 2004, and
> it is protocol-aware for http (port 80 and 443) traffic, so I can't
> think of a way to block the port 443 traffic as it appears to go through
> the ISA server as a valid SSL connection, just like someone browsing an
> SSL website.
>
> I'm really stuck on this. We only allow web access on ports 80 and 443
> by corporate policy, yet a ton of our people are using this software.
> Help!
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> firewall-wizards@listserv.icsalabs.com
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>

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