WikiLeaks just published details of a purported CIA operation that turns Windows file servers into covert attack machines that surreptitiously infect computers of interest inside a targeted network.

"Pandemic," as the implant is codenamed, turns file servers into a secret carrier of whatever malware CIA operatives want to install, according to documents published Thursday by WikiLeaks. When targeted computers attempt to access a file on the compromised server, Pandemic uses a clever bait-and-switch tactic to surreptitiously deliver malicious version of the requested file. The Trojan is then executed by the targeted computers. A user manual said Pandemic takes only 15 seconds to be installed. The documents didn't describe precisely how Pandemic would get installed on a file server.

In a note accompanying Thursday's release, WikiLeaks officials wrote:

Today, June 1st 2017, WikiLeaks publishes documents from the "Pandemic" project of the CIA, a persistent implant for Microsoft Windows machines that share files (programs) with remote users in a local network. "Pandemic" targets remote users by replacing application code on-the-fly with a Trojaned version if the program is retrieved from the infected machine. To obfuscate its activity, the original file on the file server remains unchanged; it is only modified/replaced while in transit from the pandemic file server before being executed on the computer of the remote user. The implant allows the replacement of up to 20 programs with a maximum size of 800 MB for a selected list of remote users (targets). As the name suggests, a single computer on a local network with shared drives that is infected with the "Pandemic" implant will act like a "Patient Zero" in the spread of a disease. It will infect remote computers if the user executes programs stored on the pandemic file server. Although not explicitly stated in the documents, it seems technically feasible that remote computers that provide file shares themselves become new pandemic file servers on the local network to reach new targets.

“Very specific use”

CIA officials have never confirmed or refuted the authenticity of the documents released in the "Vault 7" series, which WikiLeaks claims includes confidential documents it obtained when the CIA "lost control of the majority of its hacking arsenal." Outside experts on malware, however, have said the documents appear to be legitimate. Security company Symantec has also definitively tied malware described in one Vault 7 release to a known hacking operation that has been penetrating governments and private industries around the world for years.

Documentation that accompanied Thursday's release said that Pandemic is installed as a minifilter device driver. Jake Williams, a malware expert at Rendition InfoSec, told Ars that this means Pandemic would have to be signed by a valid digital certificate that was either bought or stolen by the operative, or it means the implant would have to be installed using an exploit that circumvented code-signing requirements. The driver-signing restriction and other technical details, he said, give the impression the tool isn't in widespread use.

"This code looks like it was developed with a very specific use in mind," he said. "Many larger organizations don't use Windows file servers to serve files. They use special built storage devices (network attached storage). My guess here would be that this was designed to target a relatively small organization."

Williams, who worked in the National Security Agency's elite Tailored Access Operations hacking group until 2013, said Thursday's release appeared to omit some of the documents operatives would need to use the Pandemic implant.

"If you handed me this tool, I don't have enough information to make it go," he said. "There's more documentation than this. It's anyone's guess as to why it wasn't released."

The Vault 7 documents are a serious blow to the US intelligence community and its failed efforts to keep advanced software exploits confidential. Still, they aren't as sensitive as a separate trove of NSA hacking tools published over the past nine months by a mysterious group calling itself the Shadow Brokers . Unlike the Vault 7 materials, the latter series of leaks includes all of the underlying exploit code, giving anyone the ability to wage potent attacks that were once the sole province of the world's most sophisticated hacking operation. NSA attack tools, most of which are designed to work remotely on a wide range of computers, are generally much more advanced than the CIA counterparts, which usually are used in the field by agents who already have some level of access to targeted computers or networks.

Like previous Vault 7 releases, today's leak is a critical blow to US intelligence interests. But it's nowhere near as grave as the Shadow Brokers leaks.