> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of
> Raphael Coeffic
> Sent: Thursday, March 05, 2009 4:48 AM
>
> The second difference is that it works
> right now with any publicly reachable SIP provider.

I think I know what you mean by this statement, but maybe I don't.  I think you 
mean it "works" right now only on a publicly reachable SIP provider that 
accepts INVITE requests from non-Registered Contacts.  No?  Or do you mean 
you've done testing of all publicly reachable SIP providers and found this to 
be an issue for all of them, right now?

Since the REGISTERs are almost always challenged, this attack is not an issue 
for providers which reject INVITEs from non-Registered Contacts.  Since SBC's 
have offered that restriction policy for at least the past 5 years, and 
presumably outbound-proxies do too (because it's a very popular policy), then 
you're really only talking about a theoretical subset of publicly reachable SIP 
Providers right now.

And this is not to say the attack isn't interesting, or that publicly reachable 
SIP providers actually *use* such security policies.  I've been surprised 
before about how some of them don't actually employ the security mechanisms 
they have at their disposal.  But not using available mechanisms is very 
different from not having a way to do them.

-hadriel

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