[OpenSIPS-Users] Could I build a "SIP firewall" with OpenSIPS?

Kamen Petrov kamen.petrov at gmail.com
Sat Apr 16 19:57:43 CEST 2011

While we are on that matter.. I want to hear your opinion guys.
Despite it is opensips or something else, the fraud calls are a huge issue
now days... especially in the pinless scenarios.

Here is the problem: the DID provider sends the call in -> the call is
authenticated by caller id -> the call is processed
In that scenario the DID provider sends fake caller ID.

To handle that issue, one of my customers wants to implement this:

<http://www.trustid.com/solutions/>Looking trough their demo, this sounds
too much like science fiction to me. As far as someone is working with
caller IDs all over the world, there is no any good way to determinate if
the caller id is real or not. Up to my knowledge, the only really secured
way is to receive the incoming calls directly trough PSTN rather than VoIP.

Do you feel like me this company cannot provide what they sell or you have
any vision different than mine? Please share your opinion :)
-- Kamen*

On 14 April 2011 13:25, Anca Vamanu <anca at opensips.org> wrote:

>  Hi Dan,
> On 04/13/2011 05:43 PM, Dan Ballance wrote:
> Hi there,
>  I am investigating OpenSIPS for use in my company's VOIP network.
> I'm wondering if I could get a little advice on a design I am considering?
>  The problem:
>  We currently have a VOIP network built around a propriety SIP proxy which
> we are discovering appears to have a number of security weaknesses. The most
> significant of these is it's inability to tear down calls in progress once a
> user's balance has hit zero and having no ability to limit the channels that
> a user has open. This could potentially cripple our business due to the
> losses we are experiencing from fraud.
> You can use opensips for implementing the firewall that you require, but
> your solution is not complete. I will explain bellow why.
>  A very early draft of my solution:
>  I have noticed the OpenSIPS module userblacklist (
> http://www.opensips.org/html/docs/modules/1.6.x/userblacklist.html ) and
> believe that this could solve our problems. I have other code running
> elsewhere on our network which is able to identify fraudulent calls - I just
> need a way of killing said calls and stopping the fraud in progress. It
> seems with this module I could call a web service on the OpenSIPS server,
> add and remove SIP uris from the blacklist database table and then call the
> module MI function via XML-RPC to update the list and cut off the call. (At
> least I am hoping it could do this - can the blacklist block calls in
> progress?)
> The userblacklist module can be used to deny future calls from a fraudulent
> account. Just that you have to also provide the prefix for the destination
> that you want to block. So, from your external application you can add
> record with the account and prefixes in the *userblacklist* table and call
> the MI command 'reload_blacklist' to let opensips know that the list was
> been updated.
> But you can not use it to stop ongoing calls. For this you need the *
> dialog* module, you can tell it to stop an ongoing call by sending the MI
> command dlg_end_dlg(
> http://www.opensips.org/html/docs/modules/devel/dialog.html#id294808).
> Note that you have to call *dlg_list* 'callid' (
> http://www.opensips.org/html/docs/modules/devel/dialog.html#id294675)
> before to get the info required by *dlg_end_dlg* command.
>  Assuming the userblacklist module will do what I hope, I have a question
> about how to slot the OpenSIPS server into our network. In an ideal world, I
> would run the OpenSIPS server in stateless mode so that is scales well, and
> do nothing more with the SIP traffic apart from forward on non-blocked calls
> to our existing propriety SIP proxy and block banned SIP uris from
> progressing any further.
>  The main question I have is can the userblacklist module be run in
> stateless mode and is it possible for OpenSIPS to forward on traffic to
> another SIP proxy for registration. In effect I guess I am trying to build
> some kind of SIP firewall out of OpenSIPS but I don't know if this is
> possible. Any advice / constructive criticism from the knowledgeable people
> on this list would be massively appreciated!
>  If you use the dialog module - then you will have to have opensips
> running in statefull mode (dialog aware in fact).
>  Sincerely,
>  Dan.
>  (If it's okay I will keep my surname and company name anonymous due to
> the public nature of this list and the fraud problems that we have been
> experiencing.)
>  Regards,
> --
> Anca Vamanu
> OpenSIPS Developer
> _______________________________________________
> Users mailing list
> Users at lists.opensips.org
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