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A Vonage VOIP 3-way call CID Spoofing Vulnerability
Original Advisory: Wednesday, August 13, 2003
Severity: Medium - High
Description: An attacker using the VOIP (Voice Over IP) carrier Vonage,
has the ability to spoof the caller ID of a called party through the three-
way calling feature. This trick essentially acts similar to a POTS-based
diverter, as it allows the attacker to carry out illicit telephone
activities while hiding his or her phone number.
Version: This was tested using Cisco Systems' ATA 186 VOIP hardware on the
Author: Nathan Wosnack
"Using an existing high-speed Internet connection, Vonage technology
enables anyone to make and receive phone calls - worldwide - with a touch-
tone telephone. Offering quality phone service bundled with enhanced IP
communications services, our interactive communications portal is a
gateway to advanced features only available through digital telephone
service. Utilizing our global network and advanced routing technologies,
Vonage offers an innovative, feature-rich and cost effective alternative
to traditional telephony services."
Description of the problem:
By using SIP-enabled voice over IP (VOIP) hardware such as the Cisco ATA
186 Analog Telephone Adaptor, it's possible to spoof the caller
identification that shows up on a call. The attacker only needs to call up
a regular phone line (POTS - plain old telephone service), place the
caller on hold, flash over to a dial tone using the threeway call feature,
and then call a second party for this to work. The caller ID information
that tends to show up is the first called party's telephone number with
either their name listed or "unknown name" showing on a conventional
caller-id enabled telephone. The opportunity for abuse is high and could
allow the determined attacker to social engineer your telephone, cable, or
utility company into modifying your services. Since many companies only
require the person's name, address, and caller id for account
authentication, this vulnerability helps the attacker. The other
opportunities this vulnerability gives the attacker is the ability to
spoof anyone's caller id information for phone hacking (often
called "phreaking"); such as breaking into voice mail accounts and PBX
exploitation for the purpose of proprietary information gathering and
Solutions to the problem:
This issue is something that Vonage will need to investigate on their end.
The proper routing of caller id information after a third-party call is
initiated is the problem, and needs to be resolved by the Vonage IT staff
figuring out why their VOIP switching equipment doesn't pass this data
properly. The Hypervivid Solutions staff has contacted Vonage directly
about this issue, so it can hopefully be resolved shortly.
For everyone else, your best defense is to be aware of who is calling you.
If you happen to receive a phone call from an unknown party who wants to
place you on hold, hang up immediately and then call them back.
If you hear a recording telling you the number is not in service, then
you've likely reached a Vonage gateway number, which mean you were likely
called by someone attempting to exploit this Vonage VOIP vulnerability.
In the past year, Voice over IP telephony has seen many security issues.
The voip issues range from vendor implementations of the Session
Initiation Protocol (SIP), problems with remote-accessible code which can
be exploited to cause a denial of service, voip phones that are weak in
ways that facilitate man-in-the-middle attacks directed at intercepting
telephone traffic, and most recently 3-way caller ID spoofing on Vonage.
When the information security community works closely with vendors and
carriers, these problems can be resolved quickly and efficiently enough to
limit or even eliminate any abuse by phone phreaks and criminals.
http://www.hypervivid.com/ - Information, Telecom and Wireless Security
http://www.cisco.com/ - Cisco Systems, Inc. Manufacturer.
http://www.vonage.com/ - American Voip telecom carrier.
Have any questions or comments?
Copyright © 2003, Hypervivid Solutions Incorporated. All Rights Reserved.