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Enlarge / A computer screen displaying Eternalromance, one of the hacking tools dumped Friday by Shadow Brokers.

The people behind Tuesday's massive malware outbreak had access to two National Security Agency-developed exploits several weeks before they were published on the Internet, according to evidence unearthed by researchers from antivirus F-Secure.

On Thursday, F-Secure researchers said they have evidence that the still-unknown developers of Tuesday's NotPetya malware had access to EternalBlue and EternalRomance as early as February, when they finished work on the malware component that used the stolen NSA exploits. The timeline is all the more significant considering the quality of the component, which proved surprisingly adept in spreading the malware from computer to computer inside infected networks. The elegance lay in the way the component combined the NSA exploits with three off-the-shelf tools including Mimikatz, PSExec, and WMIC. The result: NotPetya could infect both patched and unpatched computers quickly. Code that complex and effective likely required weeks of development and testing prior to completion.

"February is many weeks before the exploits EternalBlue and EternalRomance (both of which this module utilizes) were released to the public (in April) by the Shadow Brokers," F-Secure researcher Andy Patel wrote in a blog post. "And those exploits fit this component like a glove."

Whereas the two other main components of NotPetyaan encryption component and a component for attacking a computer's master boot recordwere "pretty shoddy and seem kinda cobbled together," Patel said the spreading component seems "very sophisticated and well-tested." For developers to finish work on the spreader by February, they clearly had the NSA exploits in hand by then. By contrast, Patel added:

WannaCry clearly picked [the NSA] exploits up after the Shadow Brokers dumped them into the public domain in April. Also WannaCry didn't do the best job at implementing these exploits correctly.

By comparison, this "Petya" looks well-implemented, and seems to have seen plenty of testing. It's fully-baked.

The weeks leading up to February's completion of the NotPetya spreader was a particularly critical time for computer security. A month earlier, the Shadow Brokers advertised an auction that revealed some of the names of the exploits they had, including EternalBlue. NSA officials responded by warning Microsoft of the theft so that the company could patch the underlying vulnerabilities. In February, Microsoft abruptly canceled that month's Patch Tuesday. The unprecedented move was all the more odd because exploit code for an unpatched Windows 10 flaw was already in the wild and Microsoft gave no explanation for the cancellation.

"Meanwhile, 'friends of the Shadow Brokers' were busy finishing up development of a rather nifty network propagation component, utilizing these exploits," Patel wrote.

When Patch Tuesday resumed in March, Microsoft released a critical security update that fixed EternalBlue. As the WCry outbreak would later demonstrate, large numbers of computersmainly running Windows 7failed to install the updates, allowing the worm to spread widely.

If the timeline is correct, it would mean the NotPetya developers had some sort of tie to the Shadow Brokers, possibly as customers, colleagues, acquaintances, or friends. It would also make NotPetya the first piece of in-the-wild malware that had known early access to the NSA exploits. Patel didn't say how the NotPetya developers got hold of EternalBlue and EternalRomance prior to their public release in April.

Early speculation was that Shadow Brokers members acquired a small number of hacking tools that NSA personnel stored on one or more staging servers used to carry out operations. The volume and sensitivity of the exploits and documents released over the next several months slowly painted a much grimmer picture. It's now clear that the group has capitalized on what is likely the worst breach in NSA history. There's no indication the agency has identified how it lost control of such a large collection of advanced tools or that it knows much at all about the Shadow Brokers' membership. The group, meanwhile, continues to publish blog posts written in deliberately broken English, with the most recent one on Wednesday.

The F-Secure evidence adds a new unsettling entry on the Shadow Brokers' resume. The world already knew the group presided over a breach of unprecedented scope and leaked exploits to the world. Now, we know it also provided crucial private assistance in developing one of the most virulent worms in recent memory.

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NotPetya developers obtained NSA exploits weeks before their public leak - Ars Technica