Instead, Kamluk saw that it was a self-spreading piece of code with very different intentions. Using what was referred to within the code as “wormlet” functionality, Fast16 is designed to copy itself to other computers on the network via Windows’ network share feature. It checks for a list of security applications, and if none are present, installs the Fast16.sys kernel driver on the target machine.

That kernel driver then reads the code of applications as they’re loaded into the computer’s memory, monitoring for a long list of specific patterns—“rules” that allow it to identify when a target application is running. When it detects the target software, it carries out its apparent goal: silently altering the calculations the software is running to imperceptibly corrupt its results.

“This actually had a very significant payload inside, and pretty much everybody who looked at it before had missed it,” says Costin Raiu, a researcher at security consultancy TLP:Black who previously led the team that included Kamluk and Guerrero-Saade at Russian security firm Kaspersky, which did early work analyzing Stuxnet and related malware. “This is designed to be a long-term, very subtle sabotage which probably would be very, very difficult to notice.”

Searching for software that met the criteria of Fast16’s “rules” for an intended sabotage target, Kamluk and Guerrero-Saade found their three candidates: the MOHID, PKPM, and LS-DYNA software. As for the “wormlet” feature, they believe that the spreading mechanism was designed so that when a victim double-checks their calculation or simulation results with a different computer in the same lab, that machine, too, will confirm the erroneous result, making the deception all the more difficult to discover or understand.

In terms of other cybersabotage operations, only Stuxnet is remotely in the same class as Fast16, Guerrero-Saade argues. The complexity and sophistication of the malware, too, place it in Stuxnet’s realm of high-priority, high-resource state-sponsored hacking. “There are few scenarios where you go through this kind of development effort for a covert operation,” Guerrero-Saade says. “Somebody bent a paradigm in order to slow down or damage or throw off a process that they considered to be of critical importance.”

The Iran Hypothesis

All of that fits the hypothesis that Fast16 might, like Stuxnet, have been aimed at disrupting Iran’s ambitions of building a nuclear weapon. TLP:Black’s Raiu argues that, beyond a mere possibility, targeting Iran represents the most likely explanation—a “medium-high confidence” theory that Fast16 was “designed as a cyber strike package” that targeted Iran’s AMAD nuclear project, a plan by the regime of Ayatollah Khameini to obtain nuclear weapons in the early 2000s.

“This is another dimension of cyberattacks, another way to to wage this cyberwar against Iran’s nuclear program,” Raiu says.

In fact, Guerrero-Saade and Kamluk point to a paper published by the Institute for Science and International Security, which collected public evidence of Iranian scientists carrying out research that could contribute to the development of a nuclear weapon. In several of those documented cases, the scientists’ research used the LS-DYNA software that Guerrero-Saade and Kamluk found to have been a potential Fast16 target.