More disclosures about Canada's aggressive foreign spying activities are coming, suggests Glenn Greenwald, the American journalist revealing the top-secret documents acquired by Edward Snowden, the former U.S. National Security Agency employee and security contractor.

"There is a huge amount of stuff about Canada in these archives because Canada works so closely with the NSA," Mr. Greenwald, who lives in Brazil, told The Globe and Mail in an interview on Monday.

While he said that he would not comment on documents not yet made public, he said that Canadians should know that "there is nothing really unique about what Canada's doing to Brazil – it's not like Brazil is the only target for Canada."

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On Sunday, Mr. Greenwald teamed with reporter Sonia Bridi from Brazil's flagship investigative television program Fantastico to reveal documents suggesting that the Communications Security Establishment of Canada (CSEC), an ultrasecretive "electronic-eavesdropping agency," set out to conduct a cyber-espionage campaign against Brazil's mines and energy ministry.

Brazil's president Dilma Rousseff called the spying "unacceptable" on Twitter Monday. Saying the spying appeared to be a clear case of industrial espionage, she demanded an explanation from the Canadian government.

The leaked documents suggest that in 2012 CSEC used a spying program code-named Olympia to map the phone calls, e-mails and video conferences made within the mines and energy ministry.

Mr. Greenwald said that Brazil isn't the only country that the Olympia program has targeted, according to the documents he has seen. He added that the ramifications spread far beyond Brazil.

"The reason this is so newsworthy is that the U.S. and its allies love to say the only reason they are doing this kind of mass surveillance is they want to stop terrorism and protect national security – but these documents make clear it is industrial and economic competition, it's about mining resources and minerals," Mr. Greenwald said.

Last month, Mr. Greenwald and Globo revealed that the NSA is spying on Petrobras, Brazil's national oil company.

Mr. Greenwald says its hypocrisy that the United States and its allies publicly lament they are victims of cyber-espionage while privately engaging in such intelligence-gathering campaigns themselves.

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"The U.S. is running around publicly accusing China of using hacking for industrial advantage – well, this is a really clear cut example of this – of how Canada and the rest of the Five Eyes are doing it," he said.

The "Five Eyes" is the name for the secretive alliance of "signals-intelligence" agencies from the English-speaking world – Australia, Britain, Canada, New Zealand, and the United States – that has existed since the Second World War. For decades countries have had a loose agreement to help each other spy on foreign countries, while refraining from spying on one another.

Mr. Greenwald said the revelations about CSEC he worked to broadcast on Fantastico on Sunday night stood out among the documents in the Snowden archive that he has reviewed so far.

"It was a pretty amazingly detailed document, given what these documents usually are."

He wryly quipped that it was characteristically Canadian – "polite and thoughtful" – for the spy agency to have made its activities so explicit.

When the reporting team took the CSEC-stamped documents to Brazil's Ministry of Mines and Energy for a response, officials immediately latched on to their significance.

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"The Brazilians were very specific about the competition they're in with Canada and Canadian industry and the interest the industry has in Brazil," Mr. Greenwald said. "And pretty indignant about how obvious the motive is, purely for industrial and economic advantage."

One of the leaked slides makes it clear CSEC collaborates with the U.S. National Security Agency's highly aggressive "Tailored Access Operations" unit.

"TAO is one of the most aggressive and insidious parts of the NSA – they're hackers – they hack other people's computers exactly the way hackers that the U.S. puts in prison do," Mr. Greenwald said. "Canada is working with the NSA on some of the most aggressive techniques that the NSA did."

Mr. Greenwald first met with Mr. Snowden in Hong Kong along with filmmaker Laura Poitras last summer. The former contractor had reached out to them, explaining that he had amassed a treasure trove of classified NSA and allied material that he wanted to leak.

Mr. Greenwald said that when he and Ms. Poitras began to learn what was in the documents, they were struck by "how active Canada is in its partnership with the U.S. and U.K."

Mr. Snowden now lives in Moscow, out of the reach of U.S. authorities who are seeking to try him on espionage charges.