As online security gradually improves, the security of telephone based services has either stagnated or actually deteriorated. The old maxim of a chain being only a strong as it’s weakest link is sitting in eager anticipation of again being proven correct.

The problems can be split into some broad classifications:

i) the protection against replay attacks that (most) banks use for their online services are not used over the telephone;

ii) authentication credentials are often shared between strong online and weak phone services;

iii) static personal details are used as part of the authentication process over the telephone;

iv) there is an invalid assumption made that the phone call is private and secure;

v) telephone requests tend to “trump” anything done via online services;

vi) unsolicited calls are made from banks to customers that require only the customer to authenticate;

vii) catch phrases are overriding common sense.

The first problem highlighted above, (i), can be illustrated by example. Most banks request only a subset of a “PIN” or password when authenticating to an online banking service, however over the phone almost all banks ask for the full login credentials. For example, the Co-operative Bank has recently improved it’s online security immensely: logins only request a subset of details, there is a second stage of authentication whereby a random selection of one of four preset questions are asked, and most importantly before any transaction can be performed it must be authenticated via a smart card + card reader device. However, upon phoning, the automated service immediately asks for the full PIN. The problem is exacerbated by (iv), specifically that online services are at least encrypted using SSL/TLS, however phone calls are easily tapped if the attacker is physically in the local area.

The second problem, (ii), has some not-so-subtle ramifications. If a phone call to a bank’s customer services is monitored by an attacker, they will often have the credentials necessary to login online. From an anonymity point of view, it would be much more favourable for an attacker to action transactions using the online service as opposed to the telephone service.

The third problem, (iii), is that most telephone services use an automated system that verifies account number against “PIN” or password, then passes the call onto a real advisor. At this point, the advisor will attempt to further confirm the callers identity by asking the standard “name, address, postcode, date of birth” questions. Unfortunately, unless you are the Messiah, things like date of birth won’t change that often. So considering that these details are usually easy to come by and are exposed over an unsecure line anyway, it is worrying that so much trust is placed in them.

The fourth problem, (iv), is that most banks, government departments, etc assume that the telephone is a secure method of communication. It is not. Technologically, it is trivial to tap a person’s phone line. I have lost count of the amount of very personal details and information that I have had no choice but to submit over the phone.

The fifth problem, (v), is that once you’ve authenticated yourself to a bank or similar institution over the phone – they will usually action almost anything. So if an attacker has managed to garner your authentication credentials from previous phone calls, they will pretty much have carte-blanche.

Now onto (vi). This is probably the most concerning development. In the last six months I have had a bank, a utility company, and several other similar institutions phone me without my prior request, then ask me to authenticate myself to them. Each time I have illustrated that I do not know who they are, and they they could be a complete stranger calling to obtain my details. Out of the lot of them, the only one to both understand what I was saying and to be able to appropriately authenticate themselves to me first was Scottish Power.

The last one is more insidious than it first appears, (vii). When I challenged the customer services representatives over (vi), the response I got to every question was “but it’s Data Protection”. It was obvious that the person on the other end of the phone understood what I was saying but it seems company policy generally overrides the security beneficial attribute of common sense. So the public are now left trying to swallow a bunch of meaningless catch phrases like “data protection” and “passing security”: I wonder how many of the people writing the guidelines for these departments has ever read the contents of the Data Protection Act.

There are of course mitigating factors. The two that come to mind are using a 3G mobile which has half decent encryption as standard for (iv), and caller id for (vi). However these are not always available and are not addressing the core problems: namely that trust in the security of phone services are vastly over estimated.

Ah well, rant over.

UPDATED 12th April 2010: Added [] extra meaning in title; changed author.

This sad state of affairs is pretty much what we’ve got as far as web and email security these days.  The recent proof of concept that created a real rogue CA certificate using MD5 collisions is a prime example. Everybody has known for quite some time now that MD5 is not collision resistant, it is so broke that collisions can be found within minutes on any standard desktop or laptop. That combined with the normal issues that arise with the use of HTTPS as I discussed previously really does leave web security in a sorry state of affairs.

There are sites that use decent certificate authorities (the ones that issue their certs using the SHA family and do more thorough checks before issuing a cert in the first place), and also implement HTTPS in a proper and secure manner. Most financial institutions, for example, follow good practice. Unfortunately, banks and financial institutions have also tacitly instilled a sense of trust amongst the web user. We assume online banking is secure, and online banking uses SSL/TLS: so other sites that use SSL/TLS must also be secure – and there-in lies the problem. It is in part why phishing sites work so well, we know our online banking is secure and the website in front of me is my online banking site… well, er, it certainly looks the same. How many times have you actually read and checked the warning your browser periodically spits out about certificate validity? For me its 50/50 at best, and I know better.

A fine example of this misplacement of trust was no better demonstrated than in a conversation I had the other day. The conversation in question was about how PGP public keys are exchanged. I’d highlighted that you have to get the fingerprint verified (either in person, over the phone, or by a trusted third-party keysign) before accepting or signing someone else’s public key. The response I received was somewhat dismissive – and this was from a group of information security professionals. Missing that one critical step may seem insignificant but it completely defeats the entire security model, hence rendering the use of cryptography in that situation nothing more than a big padlock on a wobbly garden shed.

So what’s my point? Firstly, technologies that employ the use of cryptography have to do it properly, or not at all. This blasé, half-assed, approach by developers and users alike is actually harmful; it takes hard earned trust from one area and transfers it into a wide-spread false sense of security. The second and more important point is that developers and system designers really need to shoulder much more of the responsbility. It’s not your email provider that’s going to have to deal with the fall-out of your account being hacked, it’s you. The business that’s purchased a cert from a CA that uses MD5 and had a load of their customers defrauded will have its reputation in gutter while the CA sits pretty.

The result of this is that its in our hands. If our browser spits out a warning about a site certificate, check it and find out why, then promply complain to the company in question. If your webmail provider isn’t using SSL/TLS properly then complain, if it’s not fixed then move providers. Probablty the best example of what end users screaming about an issue en masse can do is with Microsoft: for years their products were pretty bad in the security stakes, I would argue that there have been vast improvements since.

UPDATED 12th April 2010: Added [] extra meaning in title.