Glenn Greenwald achieved fame and notoriety last year as the Guardian columnist who broke the story of former U.S. National Security Agency contractor Edward Snowden and his vast cache of Top Secret documents.

Now, the American journalist, based in Brazil, continues to reveal how states conduct surveillance through The Intercept, a billionaire-backed online publication he co-edits. And he seems to have a new source inside the U.S. intelligence community that has helped him piece together how states are keeping tabs on allies and adversaries alike.

Mr. Greenwald spoke to The Globe and Mail ahead of a talk with Editor-in-Chief David Walmsley Tuesday, sponsored by The Canadian Journalism Foundation.

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The Canadian government is about to announce new spy legislation with anticipated language securing "Five Eyes" intelligence exchanges.

They [Canada, the U.S., Britain, Australia and New Zealand] end up supporting each others' policies in all sorts of ways, including ways that if they were to think about explicitly supporting, they would be horrified to do. I think that is the case with Canadians as well. … it's the reason the Canadians ended up paying Maher Arar all that money [$10-million], because of the complicity of the government in detaining him. That's very much what the Five Eyes network is – sharing information about your own citizens, and you don't have control over what is done with it by the other governments.

A benefit for Canada is that Five Eyes member states aren't supposed to spy on each other.

Generally, governments are more interested in having their own citizens surveilled than other citizens. This idea of 'Don't worry you're being separated out from the global spying net' is really mythical. A big part about what the Five Eyes alliance is about is that each agency develops technological methods for improving spying, for expanding surveillance capabilities and reach – which means [Communications Security Establishment Canada] is helping the other four agencies do their spying.

You write you almost blew it with Snowden because one of the impediments was familiarizing yourself with the technologies to communicate with him.

People ask me: "Are you embarrassed by it? I'm not. The reality is that every serious national-security journalist in the United States at that time, and even after, was similarly ignorant, if not more so, than I was about the need for security in communications. Now, it's almost never the case that any serious journalist e-mails me without encryption.

How much deference do you give to governments who say, "We need this stuff kept secret for national security?"

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What keeps me up at night is the opposite criticism. My bigger worry is the archive is so large. There are so many stories left to be reported.

The complaint that we haven't published enough is much more valid. There are some big countries, like Canada, that have had little reporting.

One of the things we haven't had in Canada yet is a PRISM-style disclosure showing us that corporations are in on the spying. Is that something you think is likely?

The most closely guarded secrets, tellingly, are the corporate partners.

It would astonish me if Canadian companies, Internet companies, didn't co-operate with CSEC in all sorts of ways.

But I can't say definitively whether that is true because I haven't done any reporting on that yet.

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In Citizenfour [the soon-to-be released documentary about the Snowden leaks] there's a scene suggesting you have a second leaker.

We very, very carefully analyzed every word that was on screen and we disclosed what we could disclose. Obviously, there is a really difficult environment in the U.S. with any kind of leaks. The government took the initiative and came out publicly and said they think there is another source that's leaking to us.

This interview has been condensed and edited