Australia's electronic espionage agency has exploited weaknesses in a mobile browser used by hundreds of millions worldwide and planned to hack into smartphones through data links to the Google and Samsung app stores, a leaked top secret intelligence document has revealed.

The Australian Signals Directorate (ASD) and its "Five Eyes" signals intelligence partners in the United States, Britain, Canada and New Zealand have been engaged in close collaboration to target the UC Browser, an app used by more than 500 million people, mainly in China and India and across south-east Asia, the Middle East, Africa and Russia.

UC Browser revelations: US whistleblower Edward Snowden. Credit:AFP

A 2012 United States National Security Agency (NSA) document, leaked by former intelligence contractor Edward Snowden and published by The Intercept website and the Canadian Broadcasting Corporation, shows that the ASD has played a leading role in efforts to exploit the UC Browser after it was secretly discovered to be leaking details about its users through data connections to app marketplace servers operated by Samsung and Google.

The top secret project was pursued by a joint electronic eavesdropping unit called the Network Tradecraft Advancement Team, which includes signals intelligence experts from the ASD, NSA, Britain's Government Communications Headquarters (GCHQ), Canada's Communications Security Establishment (CSE) and New Zealand's Government Communications Security Bureau (GCSB).