Stuxnet and collateral damage

To update von Clausewitz’s maxim for contemporary times: “Malware is the continuation of politics by other means.” This is one of the lessons from the ongoing Stuxnet debate: targeted computer attacks has become part and parcel of nation states’ arsenal in carrying out foreign policy objective.

There have been solid technical analysis of Stuxnet’s complex inner workings, but the debate on policy implications is starting in earnest now. One question that has been overlooked is the extent of collateral damage tolerable from carrying out this type of attack.

Stuxnet was the odd combination of both being targeted very precisely and casting an extremely wide net. The malicious payload that infected industrial controllers only kicked into gear when it detected a very specific environment, believed to represent the uranium enrichment plant operating in Iran. On the other hand, because the software development for such critical facilities typically takes place behind air-gapped networks, the worm had to be released into the wild. Its humble beginnings were no different than the self-propagating malware that wreaked havoc in the past: Code Red, Nimda, Blaster, Slammer, … Except Stuxnet was light-years ahead of its predecessors in terms of sophistication and sheer number of different vectors used to infect new targets.

Because it was after a very specific target that would not be reachable directly from the Internet, the designers threw the kitchen sink at the problem, including an exploit that allowed the malware to propagate by USB drives between machines. This meant Stuxnet would eventually reach places that vanilla malware does not, including compartmentalized networks that been assumed to be isolated from the warzone that is the Internets. Stuxnet was designed to explore every nook and cranny in that space, in pursuit of its ultimate target, the programmable logic controllers destined to spin enrichment centrifuges. Given its non-discriminatory approach to spreading, it is surprising that most of the infections remained contained in Iran, with a smaller number in Indonesia and India– countries starting with “I” apparently did not fare well. By comparison the number of infections in the US were not significant. The first question then is what other systems are “fair game” on the way to reaching an objective. Stuxnet case is complicated by the fact that the presumed target is not directly reachable. Intermediate stepping stones are required to get there, which may end up being personal computers, Internet cafes, anything that is ultimately connected to the persons of interest in some unexpected six-degrees-of-separation logic. (This brings to mind the quote from Robert H. Morris Sr: “To a first approximation, every computer in the world is connected with every other computer.”) Worse the connections are not known in advance: it is a massively parallel search, exploring every possible path along the way in hopes that one may cross paths with the actual target. Such expansive views on scope risk turning every machine in the world into collateral damage in the name of reaching the destination.

The second dimension concerns damage. On most machines it infected, Stuxnet did nothing but propagate to other targets. Again there is a similarity to the massive worm outbreaks of good old days– with the exception of Witty, most contained no malicious payload. Even if it happened to land on a computer where some unlucky engineer had been tasked with developing software for industrial controllers for an unrelated industry, the tampered product would likely have worked flawlessly for its intended environment. This is not to say that there was no cost to Stuxnet for those in its path: there is still time and productivity wasted on removing the malware from the system, both for individuals and companies.  On the other hand, economic impact for software vendors is murky. Antivirus vendors benefit from trumping up scare stories. This one fits the bill perfectly, complete with cloak-and-dagger nation state implications. Similarly it is difficult to argue that MSFT suffered great expense in addressing the vulnerabilities implicated in Stuxnet, considering their leisurely patch schedule in the presence of known 0-days.

In any case, it is misleading to focus on the designers’ intent in not harming systems– far from being a magnanimous gesture on their part, it was simply following best-practices in malware design. Noisy/buggy malware is the one that gets noticed and removed. Stealth is a survival strategy: even run-of-the-mill keystroker recorders designed to be steal credit cards in the name of petty theft strive to be very stable. Vandalizing user data, blue-screening the system or displaying in-your-face popup advertisments is the surefire way to get your malware noticed by an AV vendor. (Interesting enough Stuxnet was noticed by Kaspersky and filed away as vanilla malware a full year before its inner workings were properly understood.) The problem is that modern operating systems are incredibly complex, and it is not possible to ensure that malware lives up to its promise of zero collateral damage. When Robert Morris Jr. released the Internet worm, he intended it to propagate only, with no malicious payload and barely noticeable load on infected systems. But a slight miscalculation/bug in the logic caused it to overwhelm networks and machines. Even MSFT can not ship software updates without breaking users in some unexpected, obscure configuration– and they have much higher Q&A expertise and test matrix then organizations developing malware.

The network infrastructure has long been a battle ground, with participants of every scale from hobbyist vandals to organized crime groups and nation states, duking it out with packets. The question raised by Stuxnet is whether these frontlines will expand to includes the machines owned/used by ordinary citizens, turning them into dispensable pawns in pursuit of an elusive objective.


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