IN EARLY DECEMBER 2016, Adam was doing what he’s always doing, somewhere between hobby and profession: looking for things that are on the internet that shouldn’t be. That week, he came across a server inside New York University’s famed Institute for Mathematics and Advanced Supercomputing, headed by the brilliant Chudnovsky brothers, David and Gregory. The server appeared to be an internet-connected backup drive. But instead of being filled with family photos and spreadsheets, this drive held confidential information on an advanced code-breaking machine that had never before been described in public. Dozens of documents spanning hundreds of pages detailed the project, a joint supercomputing initiative administered by NYU, the Department of Defense, and IBM. And they were available for the entire world to download.

The supercomputer described in the trove, “WindsorGreen,” was a system designed to excel at the sort of complex mathematics that underlies encryption, the technology that keeps data private, and almost certainly intended for use by the Defense Department’s signals intelligence wing, the National Security Agency. WindsorGreen was the successor to another password-cracking machine used by the NSA, “WindsorBlue,” which was also  documented in the material leaked from NYU and which had been previously described in the Norwegian press thanks to a document provided by National Security Agency whistleblower Edward Snowden. Both systems were intended for use by the Pentagon and a select few other Western governments, including Canada and Norway.

Adam, an American digital security researcher, requested that his real name not be published out of fear of losing his day job. Although he deals constantly with digital carelessness, Adam was nonetheless stunned by what NYU had made available to the world. “The fact that this software, these spec sheets, and all the manuals to go with it were sitting out in the open for anyone to copy is just simply mind blowing,” he said.

He described to The Intercept how easy it would have been for someone to obtain the material, which was marked with warnings like “DISTRIBUTION LIMITED TO U.S. GOVERNMENT AGENCIES ONLY,” “REQUESTS FOR THIS DOCUMENT MUST BE REFERRED TO AND APPROVED BY THE DOD,” and “IBM Confidential.” At the time of his discovery, Adam wrote to me in an email:

All of this leaky data is courtesy of what I can only assume are misconfigurations in the IMAS (Institute for Mathematics and Advanced Supercomputing) department at NYU. Not even a single username or password separates these files from the public internet right now. It’s absolute insanity.

The files were taken down after Adam notified NYU.

Intelligence agencies like the NSA hide code-breaking advances like WindsorGreen because their disclosure might accelerate what has become a cryptographic arms race. Encrypting information on a computer used to be a dark art shared between militaries and mathematicians. But advances in cryptography, and rapidly swelling interest in privacy in the wake of Snowden, have helped make encryption tech an effortless, everyday commodity for consumers. Web connections are increasingly shielded using the HTTPS protocol, end-to-end encryption has come to popular chat platforms like WhatsApp, and secure phone calls can now be enabled simply by downloading some software to your device. The average person viewing their checking account online or chatting on iMessage might not realize the mathematical complexity that’s gone into making eavesdropping impractical.

The spread of encryption is a good thing — unless you’re the one trying to eavesdrop. Spy shops like the NSA can sometimes thwart encryption by going around it, finding flaws in the way programmers build their apps or taking advantage of improperly configured devices. When that fails, they may try and deduce encryption keys through extraordinarily complex math or repeated guessing. This is where specialized systems like WindsorGreen can give the NSA an edge, particularly when the agency’s targets aren’t aware of just how much code-breaking computing power they’re up against.

Adam declined to comment on the specifics of any conversations he might have had with the Department of Defense or IBM. He added that NYU, at the very least, expressed its gratitude to him for notifying it of the leak by mailing him a poster.

While he was trying to figure out who exactly the Windsor files belonged to and just how they’d wound up on a completely naked folder on the internet, Adam called David Chudnovsky, the world-renowned mathematician and IMAS co-director at NYU. Reaching Chudnovsky was a cinch, because his entire email outbox, including correspondence with active members of the U.S. military, was for some reason stored on the NYU drive and made publicly available alongside the Windsor documents. According to Adam, Chudnovsky confirmed his knowledge of and the university’s involvement in the supercomputing project; The Intercept was unable to reach Chudnovsky directly to confirm this. The school’s association is also strongly indicated by the fact that David’s brother Gregory, himself an eminent mathematician and professor at NYU, is listed as an author of a 164-page document from the cache describing the capabilities of WindsorGreen in great detail. Although the brothers clearly have ties to WindsorGreen, there is no indication they were responsible for the leak. Indeed, the identity of the person or persons responsible for putting a box filled with military secrets on the public internet remains utterly unclear.

An NYU spokesperson would not comment on the university’s relationship with the Department of Defense, IBM, or the Windsor programs in general. When The Intercept initially asked about WindsorGreen the spokesperson seemed unfamiliar with the project, saying they were “unable to find anything that meets your description.” This same spokesperson later added that “no NYU or NYU Tandon system was breached,” referring to the Tandon School of Engineering, which houses the IMAS. This statement is something of a non sequitur, since, according to Adam, the files leaked simply by being exposed to the open internet — none of the material was protected by a username, password, or firewall of any kind, so no “breach” would have been necessary. You can’t kick down a wide open door.

The documents, replete with intricate processor diagrams, lengthy mathematical proofs, and other exhaustive technical schematics, are dated from 2005 to 2012, when WindsorGreen appears to have been in development. Some documents are clearly marked as drafts, with notes that they were to be reviewed again in 2013. Project progress estimates suggest the computer wouldn’t have been ready for use until 2014 at the earliest. All of the documents appear to be proprietary to IBM and not classified by any government agency, although some are stamped with the aforementioned warnings restricting distribution to within the U.S. government. According to one WindsorGreen document, work on the project was restricted to American citizens, with some positions requiring a top-secret security clearance — which as Adam explains, makes the NYU hard drive an even greater blunder:

Let’s, just for hypotheticals, say that China found the same exposed NYU lab server that I did and downloaded all the stuff I downloaded. That simple act alone, to a large degree, negates a humongous competitive advantage we thought the U.S. had over other countries when it comes to supercomputing.

The only tool Adam used to find the NYU trove was Shodan.io, a website that’s roughly equivalent to Google for internet-connected, and typically unsecured, computers and appliances around the world, famous for turning up everything from baby monitors to farming equipment. Shodan has plenty of constructive technical uses but also serves as a constant reminder that we really ought to stop plugging things into the internet that have no business being there.

The WindsorGreen documents are mostly inscrutable to anyone without a Ph.D. in a related field, but they make clear that the computer is the successor to WindsorBlue, a next generation of specialized IBM hardware that would excel at cracking encryption, whose known customers are the U.S. government and its partners.

Experts who reviewed the IBM documents said WindsorGreen possesses substantially greater computing power than WindsorBlue, making it particularly adept at compromising encryption and passwords. In an overview of WindsorGreen, the computer is described as a “redesign” centered around an improved version of its processor, known as an “application specific integrated circuit,” or ASIC, a type of chip built to do one task, like mining bitcoin, extremely well, as opposed to being relatively good at accomplishing the wide range of tasks that, say, a typical MacBook would handle. One of the upgrades was to switch the processor to smaller transistors, allowing more circuitry to be crammed into the same area, a change quantified by measuring the reduction in nanometers (nm) between certain chip features. The overview states:

The WindsorGreen ASIC is a second-generation redesign of the WindsorBlue ASIC that moves from 90 nm to 32 nm ASIC technology and incorporates performance enhancements based on our experience with WindsorBlue. We expect to achieve at least twice the performance of the WindsorBlue ASIC with half the area, reduced cost, and an objective of half the power. We also expect our system development cost to be only a small fraction of the WindsorBlue development cost because we carry forward intact much of the WindsorBlue infrastructure.