WikiLeaks has claimed that CIA hackers are entering and travelling through Europe undetected by posing as diplomats with 'black' passports.

In its latest release of confidential documents, the anti-secrecy organisation led by Julian Assange alleged that the CIA is using the US consulate in Frankfurt as a covert base for hackers.

WikiLeaks claimed the hackers are given diplomatic ('black') passports and State Department cover while they're involved in operations in Europe, the Middle East and Africa.

It was claimed that in order to "breeze through German Customs" the hackers are instructed to tell border officials that they have flown to Frankfurt to support "technical consultations" at the consulate in Germany's financial hub.

The Central Intelligence Agency (CIA) (
Image:
Getty)

WikiLeaks said: "Once in Frankfurt CIA hackers can travel without further border checks to the 25 European countries that are part of the Shengen [sic] open border area - including France, Italy and Switzerland."

WikiLeaks claimed the hackers are instructed beforehand to memorise their cover story, and avoid leaving electronic devices or any sensitive material unattended in their hotel room.

The alleged CIA document reminds agents that all of their colleagues are undercover, and they should avoid work discussions outside the consulate - known internally Center for Cyber Intelligece Europe - to avoid blowing their cover.

It also contains advice on how to withdraw cash from a local ATM, plus directions to the consulate and a reminder that many shops are closed on Sundays.

WikiLeaks founder Julian Assange (
Image:
PA)

The document encourages the agents to plan mini-breaks, network with their colleagues and purchase something from a duty free shop before travelling home.

It also suggests that there's an internal competition to see who can leave Germany with as little euros as possible.

WikiLeaks said it obtained a trove of documents on top-secret hacking tools used by the CIA. The documents are being published online as part of its mysterious Year Zero series.

Among the claims are allegations the CIA hacked iPhones and Microsoft Windows, and worked with MI5 to turn Samsung TVs into microphones as part of a global hacking programme.