[VOIPSEC] Voice or Not -- Fake Voice Packet???

[Roland Auckenthaler]

Hi,

A VAD would definitely e an option but what if my spoofed/faked packets
also contain voice? A VAD would still let these packets through.

From this perspective I think the question is whether somebody can
determine if the received packets are actually from the given source and
not from a different source that tries to send me unsolicited RTP
packets. 

If I would take listen to the RTP stream, I could determine the SSRC and
timestamp of the RTP and then start sending RTP packets with the
subsequent timestamps so that the original packets will be discarded
because my spoofed packets were received earlier.

Is there anything you can do about such a scenario?

roland

-----Original Message-----
From: Voipsec-bounces at voipsa.org [mailto:Voipsec-bounces at voipsa.org] On
Behalf Of Thomas Howe
Sent: 03 October 2005 19:37
To: Vijay Shyamasundar Shyamasundar; Voipsec at voipsa.org
Subject: Re: [VOIPSEC] Voice or Not -- Fake Voice Packet???


Hi Vijay - 

To a certain (practical) extent, you can.  Many coders have voice
activity detection front ends, and they could be used as a basis for an
algorithm to determine if the uncompressed packets contain stuff that
looks like voice. As I recall (and it's been a while since my DSP days),
they tend to look at energy levels and sinusoidal components.

My question is, why do you care?  If it doesn't have voice, then what's
the big deal?

Tom


-----Original Message-----
From: Voipsec-bounces at voipsa.org on behalf of Vijay Shyamasundar
Shyamasundar
Sent: Mon 10/3/2005 2:09 PM
To: Voipsec at voipsa.org
Subject: [VOIPSEC] Voice or Not -- Fake Voice Packet???
 
Hi All,
 Is there any way to find out if the packets are genuine voice packets
or
not. By looking into the Payload Type(PT) field of RTP packet, we can
say if
its audio/video.. and the codec used. What if i could generate some
packets
with that PT field showing it as audio packet while the payload contains
something else.
 I would like to know if there is a way to find out if the packet really
contains voice or not.
  Regards,
Vijay
 On 9/9/05, Dalton, Ronda L <DaltonR at state.gov> wrote:
>
> NIST has a pretty good VOIP document:
>
csrc.nist.gov/pcig/CHECKLISTS/voip-checklist-073004.doc<http://csrc.nist
.gov/pcig/CHECKLISTS/voip-checklist-073004.doc>
> It a security checklist. Not sure what level your security is but its
a
> good starting point.
>
> RD
>
>
> Date: Thu, 8 Sep 2005 10:52:04 +0100
> From: "Barry Coatesworth" <Barry.Coatesworth at express-gifts.co.uk>
> Subject: [VOIPSEC] VOIP security policy
> To: <Voipsec at voipsa.org>
> Message-ID:
>
<0535CAC7F841F241807D2701024E64B527BCDD at ukclaexc003.express.findel.co.uk
>
>
> Content-Type: text/plain; charset="us-ascii"
>
> I am currently writing some VoIP security policy, it's the first time
I
> have had to write a VoIP one.
>
>
>
> Does anyone have example Security policy/guidelines that I could use
as
> a template? Or what must essential be included would also be helpful.
>
>
>
> thanks
>
> B.
>
>
>
>
>
> _______________________________________________
> Voipsec mailing list
> Voipsec at voipsa.org
> http://voipsa.org/mailman/listinfo/voipsec_voipsa.org
>
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