Monthly Archives: April 2017

Are you prepared to face a TDOS?

Recently, DHS (US Department of Homeland Security) announced they are developing with private partners a solution to mitigate Telephony Denial of Services (TDOS) against emergency numbers and other critical phone numbers.

For the past years TDOS attacks seems to have flourish in the US. They are often used to claim a ransom to the targeted number owner.

If you have already made a Business Impact Analysis on your telephony system, your probably know how much one day of downtime might cost you. You probably have some solutions in place but, do they protect you against a TDOS?

Don’t forget to add TDOS to your list of threats if it is relevant for your business.

Further readings:

How do penalties affect your security policies effectiveness?

One of the requirements of any decent policy (and law) is having a penalty link to its non-respect. In penal law, “Nulla lege sine poena” (no law without punishment) is one of the corollary of the famous principle “Nulla crimen, Nulla poena sine lege ” (no crime, no punishment without a law).

From a behavioural point of view, it is often more efficient (and more humane) to use the carrot (and even more the intrinsic motivation to do the things right) instead of the stick. However, knowing there is a stick helps to give some consistency to the rule, some consequences. So, when we are drafting policies, we always insist on the necessity to clearly define the consequences of any non-compliance with the rules. Organizations may be fined for it, so should their employees.

It’s often a difficult part of the policies drafting process, moreover in large organization, as we must find a proportionate response and it must be, in some countries, negotiated beforehand with trade unions and social partners.

But there is more to say about it. First, the consequences mentioned are quite often individual ones: loss of privileges, impact of financial bonuses or removal from offices. Though, there is more to it. Breaking rules can lead to huge monetary losses for the organization, resulting in cost cutting and having colleagues losing their jobs, putting families in financial and personal difficulties. It’s a bigger picture; it’s not a systematic consequence, although more likely than ever, but mainly it is a foreseeable consequence that might trigger more emotional response than the one of the person’s own demise (although it might have some opposite effect if the person has a grudge against the entire company, including its workers). Emotions are leading our choices more than rationality.

The second point is that it must be fair. As suggested by Herath & rao (2009), too severe punishment will have an adverse effect and increase the likelihood of the infringement. This effect is likely similar to the one observed with the pictures of sick lunges of cigarettes pack: they tend to increase the consumption of cigarettes (mostly with young adults and adolescents).

The third point is that the rule must be the same for everybody, in theory and in effect. So, we must ensure that we can systematically detect these infringements (see Herath & Rao, 2009) to increase the compliance.

But how often do we see people in organization breaking the rules willingly without any consequence? Sometimes because this person is an expert in his/her field and we believe we need her/his knowledge more than we would. Sometimes it’s for some internal political reasons. Sometimes because (s)he’s a relative of someone high in the food chain.  Whatever the reason, this is not fair and it has some huge impact on the behaviour of your employees. Worse, it becomes part of your culture and that’s something that you will have a lot of difficulties to change after.

So, mind your punishment twice.


StartSSL is blocked by Chrome & Firefox and they didn’t notified their customers

The SSL certificates issued by Israel based Certificate Authority StartSSL ( are blocked by Google Chrome and Mozilla Firefox since March 2017. Behind what could be just a technical issue, there is some disturbing facts:

First, the reason why Google and Mozilla have decided to progressively block StartSSL (and more importantly WoSign) is the issuance by WoSign, a chinese Certificate Autority,  of multiple SSL certificate for Domains for which they didn’t received any mandate and didn’t validate the ownership of the domain by the requester. The first case to be reported to Google was GitHub, the famous Source Code repository. As WoSign had “secretely” bought StartSSL and integrated its infrastructure in its own, StartSSL has been “sentenced” to the similar distrust by most browser than its owning company.

As DNS CAA records are not used by browsers to check if the Certificate Authority of an SSL certificate for a domain is the correct one, it could have allowed someone to impersonate GitHub or at least to lure some users to a fake GitHub site (anyway, GitHub didn’t set his CAA record). Such behavior is unacceptable for any certificate issuer as trust is the cornerstone of the entire SSL certificate paradigm. Google and Mozilla’s reaction seems then proportionate. However, you can imagine the impact of such sentence. For any CA, being withdraw from the list of trusted certificates of the two main browsers is like a death penalty for the CA.

The second disturbing fact is that StartSSL failed (or decided not) to properly inform its customers. Worse, it continues to sell its Class 1 certificate despite the fact they are basically useless. That’s not the kind of commercial decision that will help restore the trust to the Israeli company, even if WoSign has defined a remediation plan aiming at giving more autonomy to StartSSL (see below).

Customers who had paid for the Enterprise Validation have lost their money and are now using blocking certificates. The only cheap and rapid solution to restore access to their website (and keeping the SSL/TLS active) is likely to use LetsEncrypt free certificates.

I don’t know what the future is but I wouldn’t recommend StartSSL to anyone anymore and I doubt any security aware person would. That’s not a good indicator for a bright future.