Voice of VOIPSA

At the IET Secure Mobile conference last week, Dr Philip Nobles from Cranfield University in the UK spoke about the subject of wireless LAN security.  He showed the output of a tool running on his laptop on a 40 mile train ride into London.  He had captured a large number of WLANs on the way, of which perhaps 60% were completely unsecured.  In addition, you could see that many were using factory default settings, for example SSIDs (LAN identifier) of ‘netgear’.  So all these sites can be compromised in terms of network sniffing, router hijhacking and theft of bandwidth.

Dr Nobles also spoke about WEP (Wired Equivalent Privacy), the first attempt to introduce encryption to WiFi networks.  I had known that WEP was compromised at least in an academic sense, but I was surprised that practical tools exist for breaking WEP in a very short time. “My router gave up its key in 3 minutes”, Nobles said of his own home router.

In view of this, here are a few ideas for securing your WLAN in the home or the office:

1. Use WPA encryption (WiFi Protected Access) if this is available on your router/client setup.  If not, use WEP in preference to leaving the router ‘open’.  Use keys (passphrases) that will not be easy to guess.

2. Most routers have an option to hide the SSID, i.e. not broadcast the name.  This means that the clients have to know the name explicitly.  This is is good idea to switch on, and makes you look much less interesting on the Netstumbler display.

3. Don’t use the default SSID, and it is better to use a name that will not be vulnerable to dictionary attack, and one that doesn’t hint at your physical location.

4. Similarly, set an admin password on your router, again one difficult to guess or get by dictionary attack.  For example, at one time I used “astro0cosmo0.”

5. Often you can block admin logon to the router from the Internet side, which is a good idea if you don’t need to remote manage it.

6. Some routers have the facility to “lock down” access to the router by only accepting connections from specific MAC addresses.  In my experience this can be inconvenient to manage (for example if a WiFi card is replaced, or if a friend comes to visit with his machine), but it does limit the options for attackers.

7. Similarly, with some routers you can assign IP addresses to specific MAC addresses, and use the firewall to block unknown IP clients.  As above, this can be inconvenient to manage, but it does limit access.

The other day at the IET Secure Mobile conference in London, Steve Babbage, Vodafone’s Group Chief Crypographer (great job title) gave the keynote, and I was fortunate to speak to him afterwards about his ideas.  One interesting area was “security through obscurity”, where he maintained that in some situations it makes sense to make an attacker’s job as difficult as possible through the use of secret algorithms.  I hope I can do the argument justice here. 

The World has changed today, and generally governments do not try to interfere in the issues of what crypto gets used in commercial mobile networks.  However, when GSM was born, 40bit encryption was a (rather weak) standard that governments agreed should be used.  In this environment, Steve Babbage maintains, the cellcos would have been mad to release all the details of the algorithm to the public, since the added obscurity would make it even harder for an attacker to get a foothold.  In the context of SIM attacks (being physically in contact with the SIM to decrypt it,  a so-called “side-channel attack”), sometimes attackers can gain knowledge about the secret key by measuring the power usage of the chip under attack.  On the other hand, if the algorithm is secret, then it is impossible for an attacker to map power fluctuations against a model, since all he has is a seemingly patternless output from an engine of unknown design. 

The use of secret algorithms is generally thought of these days as a “bad thing”, since if the algorithm is openly published it means that academics and researchers can test the thing to death and publish vulnerabilities that they find.  This should result in better algorithms and fewer defects in the long term.  Babbage doesn’t argue in favour of “cobbling something together in secret”, but rather he is saying that if you take a proven good thing like AES/Rijndael, and then add a further secret component to the algorithm, then the intellectual rigour is still there, with an added component to defeat foes.  

What do you think about security via obscurity?

CBS reports here that investigators have been given the go ahead to look at the NSA’s wire-tapping programme.

 

Clearing up around my desk the other day I found a printout of Marcus Ranum’s article, The Six Dumbest Ideas in Computer Security.  It does me good to re-read this from time-to-time, and never fails to give new ideas.  I’ve been thinking recently about viruses and spyware, and what a pain all that stuff is, so this paragraph jumped out at me:

Another place where “Default Permit” crops up is in how we typically approach code execution on our systems. The default is to permit anything on your machine to execute if you click on it, unless its execution is denied by something like an antivirus program or a spyware blocker. If you think about that for a few seconds, you’ll realize what a dumb idea that is. On my computer here I run about 15 different applications on a regular basis. There are probably another 20 or 30 installed that I use every couple of months or so. I still don’t understand why operating systems are so dumb that they let any old virus or piece of spyware execute without even asking me. That’s “Default Permit.”

This sounds perfectly sensible, doesn’t it?  Only let the good stuff run?  Of course the reason we don’t do it is that in order to select which is “the good stuff” and which is “bad”, we need a human to make a decision.  As PC users, we enjoy the flexibility to download and install anything we like, whenever we like.  I have a number of different soft-phones (Skype, SJ-Phone, Messenger, etc) that I have elected to install on my machine, and no-one else in the company was involved in the decision to do it.  Even supposing I install software from CD (for example installing firmware that comes with a VoIP phone), it is not unheard of for mass-produced software CDs to get shipped with viruses or trojans on board.  As a user, I don’t know that any particular package is “safe”, so I have to either take a risk or do without the functionality I want.

In the 1970’s there used to be a thing called the application backlog in IT which basically meant that users that wanted some kind of processing had to wait weeks, months or longer until the owners of the corporate mainframe could approve, budget, source and install some new software to solve the user need.  The PC brought with it the ability for users to solve their own problems in a timely manner, bypassing the Data Processing Manager and his domain.  However, the cost of that freedom is the risk that any package we install might include some threat which might not be apparent on day one of the install.

With PCs now being equipped for multimedia, with broadband or wireless Internet, there are more and more tempting software packages becoming available every day, ranging from mapping and route planning, to audio and movie studio software, telephony, IM and presence products.  There are many great productivity tools, offering everything from greater travel efficiency to better ways to interact with your customers. 

Of course you can lock down corporate PCs, and prevent users from installing their own software, but by using this level of control you also lose the ability for users to solve their own IT problems, and once again you are back in the world of the application backlog.

 

 

The October edition of Internet Telephony Magazine (free download can be found on the TMC website) names the 100 Top Voices of IP Communications.  A nice list of industry thought leaders, including VOIPSA Chairman, David Endler.

The same issue also has an article about CALEA, if that floats your boat. 

 

Nothing to do with VoIP, but security minded people might be interested in this.  At the Victoria & Albert Museum (V&A) in London, I saw this mechanical indicator lock:

This device has two counters integrated into the lock: one is a dummy, and the other counts the number of times that the lock has been opened, allowing you to carefully monitor access to your piles of gold, kidnapped princesses, battle plans, and other precious posessions.

It’s very easy to fall into the conceit of thinking that security is a modern concern, but devices like this have been around for centuries.

At the IP’06 event in London recently, I heard Tom Cross of Internet Security Solutions present on VoIP Security, and some of types of threats to VoIP phones.  Those of you that have listened to the Bluebox Podcast will have heard Dan York, Jonathan Zar and Shawn Merdinger talk about the threats to phone handsets before.  Some of these devices ship from the factory in an unsafe state, with security holes like remote configuration backdoors and TFTP servers running on the phone.  Often if there are usernames and passwords they can be weak combinations like ‘1′ and 1′ or ‘root’ with no password.  Often users do not know that these back doors are open, and the software does not force you to change from default or factory passwords.

The cost of not closing these security holes is that someone could remotely hack into the phone, and once in control of the phone could trace or record phone calls; mount a denial-of-service attack such as repeatedly reboot the phone; or hijack the phone in order to make calls at your cost.  So Tom’s advice was to make sure that VoIP phones are not accessible to the Internet, so they can’t be attacked from outside.

In many ways the PBX is a dinosaur these days, since it is solving problems we no longer have.  For example VoIP phones have built in dialling directories, so we don’t need a special abbreviated dialling system inside the company; VoIP softphones can have their own voicemail functionality, so we don’t need the PBX to do that.  Also traditionally, the PBX has been the device that shares out and manages the expensive, limited resources, the telco trunk lines, and increasingly PBXes don’t need to do that either, often sitting just on a LAN or LANs.  However, thinking about Tom’s words, the security aspect is a whole new reason to buy PBXes, as any device that can limit the exposure of SIP phones to attack is going to be of benefit.

 

 

 

I just stumbled across an interesting article about the use of VoIP in the battlefield. Looking at it from a security point-of-view, you can see that they have all the problems of civilian VoIP, but the consequences of failure could be much higher.

To take some examples: A successful denial-of-service attach could disable battlefield communication; Defeating the encryption system could result in eavesdropping, and the gathering of strategic intelligence; Failures in authentication could result in an enemy posing as your troops, inserting their own disinformation, or perhaps they could make accredited troops fail to attach to the voice network. Network hijacking could also be a problem, where they piggyback on your network to use its resources and equipment to pass their own data.

Certainly a lot of threats to counter. I’ve heard it said that military technology is 10 years ahead of civilian technology. I’m hoping that’s true in this case, and that there’s a lot of good stuff that we can benefit from in the next few years.

According to news in PC Pro magazine, authorities in Switzerland have come up with an unorthodox plan to tackle call tapping of Skype and other VoIP users.  VoIP calls can be end-to-end encrypted, which means that tapping on the Internet itself is often not practical.  For example Skype use an undisclosed encryption algorithm and key exchange system.  Phil Zimmermann’s Zfone employs perfect secrecy so that the conversation cannot even be listened to later offline when the encryption key has been obtained.

So the Swiss plan?  Tap the calls on the PC, by means of installing some kind of trojan to tap into the audio stream before it is encrypted.  It would be installed either by the authorities or remotely by the ISP.

Now, this is a daft idea on so many different levels that it’s hard to know where to begin.  In an ordered society like Switzerland you could expect a high level of compliance with this kind of procedure.  Unfortunately, the ones that won’t comply (for example malevolent hackers; gangsters; terrorists) are probably the ones that you are most interested in gathering intelligence about.  Secondly, it’s a gift for criminals, since if you leave a backdoor open, the PC already compromised, then someone will likely exploit this for criminal purposes.

With the right software in place, audio could be relayed in from elsewhere, allowing criminals to make calls “on your phone”, possibly implicating you in a crime.  Similarly, audio could be relayed out, so that those outside the government service could tap your phone, a boon to tabloid newspapers and blackmailers.

Finally, in a world of ever more mobile users, is this approach even practical?  Mobile users with GPRS in their phone or PDA can connect to the Internet without even touching a Swiss ISP.  Crime doesn’t necessarily stop at borders these days, couldn’t criminals just be in and out of the country before the G-Man sneaks some tapping software onto their laptop?

 

 

We’ve written here before about Phil Zimmermann’s Zfone and the ZRTP protocol, but what exactly does an encrypted phone call sound like?  Well, here is a sample, captured with Wireshark and converted to MP3 for your audio pleasure with Goldwave.

Now, if only Mr. Schwarzenegger can find a way to apply the same encryption to all of his MP3 recordings…