Sam Biddle, reporting for The Intercept: On Monday, A hacking group calling itself the "ShadowBrokers" announced an auction for what it claimed were "cyber weapons" made by the NSA. Based on never-before-published documents provided by the whistleblower Edward Snowden, The Intercept can confirm that the arsenal contains authentic NSA software, part of a powerful constellation of tools used to covertly infect computers worldwide. The provenance of the code has been a matter of heated debate this week among cybersecurity experts, and while it remains unclear how the software leaked, one thing is now beyond speculation: The malware is covered with the NSA's virtual fingerprints and clearly originates from the agency. The evidence that ties the ShadowBrokers dump to the NSA comes in an agency manual for implanting malware, classified top secret, provided by Snowden, and not previously available to the public. The draft manual instructs NSA operators to track their use of one malware program using a specific 16-character string, "ace02468bdf13579." That exact same string appears throughout the ShadowBrokers leak in code associated with the same program, SECONDDATE. SECONDDATE plays a specialized role inside a complex global system built by the U.S. government to infect and monitor what one document estimated to be millions of computers around the world. Its release by ShadowBrokers, alongside dozens of other malicious tools, marks the first time any full copies of the NSA's offensive software have been available to the public, providing a glimpse at how an elaborate system outlined in the Snowden documents looks when deployed in the real world, as well as concrete evidence that NSA hackers don't always have the last word when it comes to computer exploitation.