After taking last week off, WikiLeaks came back today and released documentation on another CIA cyberweapon. Codenamed Pandemic, this is a tool that targets computers with shared folders, from where users download files via SMB.

The way Pandemic works is quite ingenious and original, and something not seen before in any other malware strain.

Pandemic was developed for computers with shared folders

According to a leaked CIA manual, Pandemic is installed on target machines as a "file system filter driver." This driver's function is to listen to SMB traffic and detect attempts from other users to download shared files from the infected computer.

Pandemic will intercept this SMB request and answer on behalf of the infected computer. Instead of the legitimate file, Pandemic will deliver a malware-infected file instead. According to the CIA manual, Pandemic can replace up to 20 legitimate files at a time, with a maximum size of 800MB per file, and only takes 15 seconds to install. Support is include for replacing both 32-bit and 64-bit files. The tool was specifically developed to replace executable files, especially those hosted on enterprise networks via shared folders.

The role of this cyberweapon is to infect corporate file sharing servers and deliver a malicious executable to other persons on the network, hence the tool's name of Pandemic.

Detecting "patient zero" is hard, but not impossible

Once Pandemic has infiltrated a network, it's very hard to detect the source of the original infection and clean the "patient zero" host.

This is because Pandemic's file system driver will know when a local user is manually accessing one of the shared files and will execute the clean version of the file, and not the malware-laced version it delivers via SMB. In order to detect Pandemic-infected PCs, sysadmins must download and scan files from other computers via SMB (shared folders).

Section 3 of the tool's leaked manual provides a different method of detecting Pandemic malware.

Pandemic registers a minifilter driver using Windows' Flt* functions. As a result, FltMgr requires that all drivers registering as minifilters contain certain registry keys. Pandemic uses the 'Null' service key (on all Windows systems) as its own driver service key. Pandemic will create 2 sub keys and 3 values under the 'Null' service key in the registry. These values and sub keys are deleted when Pandemic is uninstalled at the end of its configured run timer, or when it is uninstalled via a special F&F (v2) DLL. These keys will NOT//NOT be deleted if the system is rebooted before the aforementioned scenarios occur.

Incident response teams who fear or suspect they might be prone to CIA surveillance can search Windows registry keys for the above minifilter drivers using Windows Flt* functions, as a sign of infection.

Today's WikiLeaks dump is part of a larger series called Vault 7, which contains documents WikiLeaks claims were stolen from the CIA by hackers and insiders. You can follow the rest of our WikiLeaks Vault 7 coverage here. Below is a list of the most notable WikiLeaks "Vault 7" dumps: