In this case Flame continues to burn Microsoft. Microsoft have announced the termination of trust of 28 additional certificates within their infrastructure in addition to the 3 that were immediately untrusted when Flame was first brought to light. This new announcement is significant as it highlights the importance of certificates within an enterprise as large as Microsoft but also highlights the interconnectedness of systems. Microsoft's announcement was based on their believe that the newly untrusted CA's are "… outside our recommended secure storage practices". What exactly that means is certainly up for discussion but Microsoft itself states that this effort is being undertaken after their continued review of what happened with Flame. This likely means that they these certificates were protected only as well as those known to be compromised and based on the form of attack there is some level of certainty that these could be exploited as well.
This interconnectivity of systems is becoming a key element of security management. When I speak of interconnectivity I do not just mean network connectivity but I also mean trust connectivity. With todays growing base of interconnected devices, whether that is the traditional server/desktop/laptop, the simple extension to mobile devices such as smartphones/tablets, or whether we take it the next level to control systems such as those interconnected through networks such as the SmartGrid or ones run by companies such as Tridium, we need to consider what happens when a security gap in one element of that infrastructure exists.
This, of course, is also not the end of the conversation. Even if we can find all those certificates and systems that Microsoft "untrusted" on all the platforms that we own and manage, this is one example of how the use of a vulnerable algorithm can create a significant and broadly impacting issue. We knew MD5, the hashing algorithm that was exploited in the original attack, was vulnerable in 2005. In fact some would rightfully argue that we knew about it almost a decade before that when flaws in the algorithm were first identified. At the time these flaws were not considered catastrophic but between 2005 and 2008 attacks against MD5 were demonstrated multiple times. It was so well understood at the time that Microsoft published a recommendation not to use MD5. In 2009 though Microsoft issued a new CA certificate using MD5. A mistake on their part but one that got through and created a significant problem.
MD5 is not the only vulnerable algorithm. Other elements of the system are also vulnerable, thankfully just not exploited yet. These other areas include one of the most commonly used hashing algorithm, SHA1, which has been theoretically shown to have a vulnerability (recognized by NIST in early 2005) but no known attacks have been shown. However the National Institute of Standards and Technology (NIST), which provides guidance for the US Government on computer security requirements, published in 2004 that SHA-1 be phased out of use in the US Government beginning in 2010. The phase out is intended to be completed by the end of 2012.
Hashing algorithms are not the only weakness. Based on the strength and availability of computing systems, 80-bit cryptography is considered vulnerable. Of course everyone will say that they do not use 80 bit keys but what NIST is saying is that algorithms with certain key sizes only provide effective security strength of 80 bits. This includes RSA-1024, DSA-1024 (with specific characteristics) and Elliptic Curve where keys are less than 224. The specific sizes of these three algorithms are again being phased out of use within the US Government as they are considered vulnerable for their common purpose. They will be completely phased out by 2013.
So yes Flame did turn up the heat on Microsoft but it also raises the overall issue of technical obsolescence of cryptographic algorithms and key sizes. This is not the first time this has happened but the major difference is that today the problem is bigger due to the interconnectedness of the systems. We now need to consider how to mitigate the threat posed here and this is where we can learn something from Flame. Flame was created as a data gatherer – the old adage of "know your enemy". We need to do the same thing and in this case the enemy is the use of vulnerable cryptographic algorithms and key sizes. Assess your environment to determine what is used and why and plan to replace those algorithms and those certificates built around vulnerable algorithms as quickly as possible.
And for those of you that think Flame is not an issue - take a look at some of my recent posts and as you read them think about Sykipot and how that has evolved over the last year. Workable exploits do not die - they evolve as our defenses do.
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