Monthly Archives: May 2010

New Book: Seven Deadliest Unified Communications Attacks

As some readers may already know, Syngress has now published a book I wrote, “Seven Deadliest Unified Communications Attacks” that dives into the threats to communications systems and the strategies to protect your systems. It is part of a series of “Seven Deadliest <topic> Attacks” books that have come out over the past couple of months. (And yes, there are seven books in the series.)

As I explained in this video, my intent was not so much to write a book about “VoIP security” but rather to take a look at a slightly larger level at the overall systems that we are connecting together under the name of “unified communications”. When we have voice, video, instant messaging, presence… coming from multiple different systems and then distributed over the global IP network… how do you secure it all?

The book was really my attempt to put in print form many of the themes we have written about on this site, talked about on the Blue Box Podcast and discussed in the VOIPSEC mailing list.

I do want to thank a couple of people in the VOIPSA circles… as I noted in the Acknowledgements, Dustin D. Trammell was an outstanding technical editor – and Andy Zmolek provided some excellent comments and thoughts. Longtime friend and VOIPSA blog contributor Martyn Davies had some helpful feedback, too, as did Scott Beer over at Ingate Systems.

Anyway, the book is out there… and I’ve put up a companion web site at www.7ducattacks.com where I’ll be listing additional resources, errata, updates, etc. There is also a Facebook page for the book. Feedback is definitely welcome (and yeah, I wouldn’t be opposed if you bought a copy or two 😉 ). I’m doing some interviews and podcasts about the book… if you are interested in interviewing me for your site or show, please contact me.

My hope with the book is that in some small way it can help encourage and spread the discussions we all have been having here… and in the end help our communications systems be a bit more secure. Thanks to all of you who have been reading posts here, commenting on them, participating in VOIPSEC and asking great questions.

P.S. If you are available tomorrow, Friday, May 20th, at 1pm US Eastern time, I’ll be interviewed live on the VoIP Users Conference call. Anyone is welcome to join in, listen, and ask questions.

Attacking the Crown Jewels through VoIP

The security weaknesses of VLANs have been known for years.  Recent case studies have highlighted the potential risk of using Voice VLANs together with VoIP in an infrastructure absent of properly configured security controls.  While visiting Europe just recently, I was reminded of this issue for a couple of reasons.

The British Crown Jewels

Firstly, I saw the magnificent British Crown Jewels in display.  They are quite impressive.  They are arguably the most valuable items in the world possessed by a sovereign state, and obviously need to be properly protected.  It really got me thinking about the origin of the term “Crown Jewels” and how the industry has used this term to refer to protection of a company’s most valuable and precious IT assets and data.  We talk about protecting against the theft of these “Crown Jewels” – a company’s IP, trade secrets, or other mission critical data.  How to protect and defend the “Crown Jewels”?

Theft of the Crown Jewels!

Hotel VoIP Deployments

After seeing the Cullinan I diamond and other precious jewels, I stayed in a hotel in Stockholm that had IP Phones deployed in guest rooms, which had me thinking again about how attackers could access a company’s IT “Jewels” from a physically unsecured area.  A quick and passive view of the IP Phone network configuration showed that this network was most likely vulnerable to the aforementioned VLAN Hop vulnerability.  I’ve been seeing an increasing amount of Hotel VoIP deployments in the last year exactly like this.

Both of these items reminded me of how easy it is for a would-be attacker, sitting in the comfort and privacy of their hotel room, to steal a company’s most valuable trade secrets and data through VoIP, in the right scenario and when the environment is not properly protected.  We’ve seen this before in production environments, in authorized security assessments.  I wanted to reach out to the community and share this with you, and see what others are seeing as well.  I’ve roughly seen 1 in 3 hotels in the past year have VoIP deployed in the guest rooms.  I am curious as to whether others are seeing a similar trend.  What other UC business applications are you seeing deployed in physically remote areas, and how are they being used?

Trunking VoIP to Physically Isolated Areas

When VoIP networks are propagated through trunk ports to physically isolated remote locations that are still under the administrative domain of the same organization, the risk increases that a VLAN Hop into the Voice VLAN can result in unauthorized access to corporate network resources.  Resources that were not intended by the system designers.  I’m making generalizations because every network is different.  But the most common configuration I am seeing takes place because the IP Phones normally need a range of TCP/UCP ports open into the call servers, and the call servers are centrally hosted on the corporate data network.  Sometimes the firewall doesn’t properly implement the policy of least privilege for only permitting operational IP Phone traffic and denying all other traffic.  The best example of a physically remote location that comes to mind is a Hotel room, but I’m sure there are other good examples.  Hotel VoIP deployments with wired ethernet offer benefits to the user such as guest VLAN Internet access from the PC port of the IP Phone.  But if you think about it, it offers the perfect backdoor attack vector into the internal network.  Privacy and seclusion.  An attacker can spend as much time as they please, evading detection and slowly discovering the network.  Each time I see this, it makes me wonder the extent to which this vulnerability is getting exploited in real life, but not being publicly disclosed.  We’ve seen how well publicized CHD / data breaches of the PCI DSS have taken place over wireless networks – I wonder if and how long it will take before this happens over a VoIP infrastructure deployed to a physically remote location which is trunked, unprotected into the internal network where mission critical servers are hosted.

Some would say that this is a network infrastructure “firewall” mis-configuration issue and not a VoIP issue.  They are right.  But you could also argue that this issue opens up only when you deploy VoIP with QoS and VoIP is so tightly integrated with the network and QoS.  The VLAN Hop also enables UC attacks against not only the IP Phones, but the call server as well.  For VoIP to be operational, those TCP/UDP ports between the IP phones and call server must always be permitted, even through a properly configured firewall.

Death of the Voice VLAN

Some have talked about the death of the Voice VLAN and others have questioned the relevance of Voice VLANs to UC Security.  In my opinion, VLANs were never intended for security.  They were designed for one thing:  Broadcast Domain isolation, resulting in improved performance and host management.  Then the “Voice VLAN” came about – a special access port feature for VoIP that enables the easy application of QoS and IP Phone provisioning.  Brilliant, if you really think about it.   Voice VLANs were also never intended for security features.  However, some started seeing it this way because, by default, a PC wasn’t a member of the Voice VLAN, and Voice would have the highest priority on the network in the event of a malware outbreak on the “data” access VLAN, and so forth.  This is still QoS – not security.  A network with properly configured QoS at layer 2 or 3 doesn’t distinguish a virus outbreak from an extremely chatty file transfer application.  In either case, VoIP will take the highest precedence through the network.  Then we started hearing “VLAN is not a security measure” and now we are coming back full circle.

Voice VLANs are never going to die off due to their perceived security limitations.  In fact, they are brilliant .  They make it easier to deploy VoIP and other new and promising UC applications, like IP Video.  Applications like IP video that are heavily reliant on QoS.  This helps us all.  The best thing we can do is recognize their security limitations and that they were never intended for security to begin with.  Which brings me to my final point.

Why?

Many of you reading this are already well aware of this.  But that doesn’t necessarily signify that others who deploy or own VoIP do as well.  Just the other day, I had a conversation with a Network Engineer who had deployed VoIP for a major US sports stadium.  This person believed that the IP Phones configured in the luxury suites were protected against VLAN Hop just because they had deployed MAC Address filtering on the switch ports.  We all know that Voice VLAN Hop and MAC Address spoofing can be automated via myriad tools.  But still, that doesn’t mean everyone else does.

I’m writing you today to ask for your help as  VoIP Security professional in spreading awareness about this issue.  I am open to hearing what you are seeing (specifically vendors and configurations in remote areas, and how the application is being used) or any other friendly comments or suggestions.  This is an area of research and interest.  Please email jostrom {at} viperlab {dot} net.

FBI Warns of New TDoS Attacks

Earlier this week, several news outlets including Wired.com reported on a new Telephony Denial-of-Service attack that’s becoming more widespread. In this attack scenario, hundreds or thousands of PSTN calls are launched to the victim’s phone in order to prevent financial institution notifications from arriving while the attacker drains accounts. It’s less clear that attackers can do anything about email or SMS alerts, but based on sheer volumes alone one has to assume the attackers are using VoIP technology to originate the calls. Certainly there are many implications to consider, particularly if TDoS attacks become more common within the PSTN going forward.

PKI Challenges and Gaps for Federation

I recently interviewed XMPP co-chair Joe Hildebrand for UCfederate.info regarding XMPP Domain Name Assertions (DNA) used to enable certain instant messaging federation use cases where an XMPP server might host multiple domains. Without DNA, it’s effectively impossible to use TLS for these multiple-domain scenarios, but that’s not the main point of this post. During the course of our conversation, we touched on the general problem of how you leverage PKI and digital certificates to establish trust between two domains for a given application protocol (itself a well-understood concept in theory) and the practical challenges that still remain on a protocol-by-protocol basis for ensuring integrity when binding a certificate to a domain for a given protocol.

Take SIP-TLS for example. We’ve run into more than a few implementations that check for a valid certificate but do absolutely no validation of the domain itself, such that if I send a message purporting to be from xyz.com after presenting a valid certificate from abc.com, not even so much as an error message is logged. Moreover, SIP doesn’t actually specify how such validation should take place, leading to vendor-proprietary implementations that utilize different certificate subject mechanisms and complicate SIP federation.

I noticed a few comments on my prior post claim that UC federation is effectively a solved problem. That’s only true if you narrow the meaning of UC federation to an absurdly small subset of the communications and collaboration space. Yes, XMPP federation for simple domain pairs for instant messaging is well defined with many interoperable vendor implementations today. Frankly, XMPP federation is the best story we’ve got for federation in the UC space, as the story degrades quickly from there. The next-best stories are effectively vendor-specific with Microsoft OCS Federation and Cisco’s Intercompany Media Engine (currently the only product using ViPR – (Verification involving PSTN Reachability – an IETF draft standard proposed by Cisco). There’s a lot of work left to do before all communications and collaboration services are federateable between enterprises, and it turns out that these certificate binding problems are one of the big gaps. To date, XMPP is the closest to solving them and the IETF is considering adopting general standards for protocol certificate binding based on related work – see: draft-saintandre-tls-server-id-check-02 for example]

There’s more to come on this topic in the near future, but for now I just want to leave you with this: it doesn’t matter how secure an established TLS connection is for a given protocol if you can’t bind application-layer domain claims with the certificate used for TLS session establishment. It’s a common fallacy that TLS “makes you secure” all by itself – that’s akin to saying that seat belts and airbags will prevent you from crashing. Federation can only succeed when all associated protocols have well-understood certificate and domain bindings that are properly validated by vendor products used by the federation participants. Anyone who tells you that’s a solved problem today for UC is delusional.