The whistleblower website said the CIA's Office of Technical Services had a biometric collection system with liaison services "with the expectation for sharing of the biometric takes collected on the systems".
But this was used to instead exfiltrate data from the systems that were provided to liaison services.
It was initially developed in 2009 and expected to remain secret until 2034.
The user guide for ExpressLane says: "ExpressLane 3.0 will overtly appear to be just another part of this system. It’s called: MOBSLangSvc.exe and is stored in \Windows\System32.
"Covertly it will collect the data files of interest from the liaison system and store them compressed and encrypted in the covert partition on a specially watermarked thumb drive when it is inserted into the system."
WikiLeaks said the main parts of the system were based on software from Cross Match, an American company that makes biometric software for law enforcement and intelligence agencies.
In 2011, the company's software was reported to have been used by the US military to identify the late Osama bin Laden during the successful bid to assassinate the Al-Qaeda leader in Abbottabad, Pakistan.