[VOIPSEC] RE: VoIP and Banking Security

[Allan Konar]

Hey Geoff/Al,
  That's not entirely true.  First of all, BPI+ is defined for use with
DOCSIS 1.1/2.0 modems.  So, if you have a DOCSIS 1.0 modem, then, at best,
you're running BPI, which is indeed very light encryption--but, that's not
the issue (and there are two severe issues in DOCSIS 1.0 BPI).  First, BPI
uses MAC address to authenticate on the TEK key exchange, which means that
spoofing of modem MAC address is all you need to get someone's TEK (Traffic
Encryption Key).

  What should make you feel better, though, is that your digits should only
be sent upstream, which means that other users on your plant would have to
have a specialized listening device.  More succinctly, since DOCSIS supports
SNMP (v1/v2c for DOCSIS 1.0 and v3 for DOCSIS 1.1/2.0) and the ifTable is a
requirement on modems and CMTS, then if a user could figure out their
(Read-Write) SNMP community, they could set ifXPromiscuousMode to 1 (true)
and dump all downstream traffic through their modem.  But, there is no tuner
in modems for listening on the upstream frequencies (remember that DOCSIS is
bi-synchronous, so modems transmit in the 5-42mhz range and listen on the
50-860mhz range).

  The issue is that BPI or BPI+ encryption is only between the CM and CMTS,
so once your tones leave the CMTS, they're open for sniffing anywhere on the
path to the bank.  If it's VoIP end-to-end, or even through another network
or two, that means that it could be vulnerable.

  Sorry for being pedantic, but I've run demos of dumping downstream traffic
on DOCSIS plants as proofs-of-concept based on this sort of misunderstanding
before.

Cheers,
a



-----Original Message-----
From: Voipsec-bounces at voipsa.org [mailto:Voipsec-bounces at voipsa.org] On
Behalf Of Geoff Devine
Sent: Thursday, June 23, 2005 8:38 AM
To: Voipsec at voipsa.org
Subject: [VOIPSEC] RE: VoIP and Banking Security

That is certainly true for any device that uses RFC 2833 DTMF Relay without
encrypting the media stream.  You really want to run something like SRTP
(RFC 3711) to encrypt media.

Something to calm your nerves:
As a Comcast customer, your DOCSIS packets are probably encrypted at your
cable modem using BPI+.  BPI+ is a fairly lightweight encryption scheme
which can be broken but that is extremely unlikely.  40-bit & 56-bit DES
encryption won't stop the NSA but it's going to discourage any hackers in
your town who can see your DOCSIS upstream. 

Geoff

- - - - - - - - - - - - - - - - - - - -
From: "Al" <alanrice at comcast.net>

Greetings,

New here, and yes, I did check the archives first.

I just finished a session with my bank using the touch pad on my phone.
When finished I dumped the packets captured during the transaction (using
ethereal).  I was a little dismayed and a lot alarmed to see wherever the
protocol was RTP EVE that the numbers I pressed on the phone were visible in
the info field:

     Payload type=RTP Event, DTMF Eight 8

I'm guessing that if I can sniff these packets, so can anyone else.

Anyone have any comments to calm my nerves?

Thanks,

Al


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