The Communications Security Establishment Canada slide presentation, published by CBC, says information was taken from wireless devices using an unidentified Canadian airport's free Wi-Fi system over a two-week period.
The May 2012 presentation suggests the project could help security officials zero in on a kidnapper based in a rural area who travelled to a city to make ransom calls.
Ottawa-based CSEC monitors foreign computer, satellite, radio and telephone traffic of people, states, organizations and terrorist groups for information of intelligence interest to Canada. It is a key player in the Five Eyes intelligence network that includes partner agencies from the United States, Britain, Australia and New Zealand.
The focus on monitoring network Internet Protocol addresses was carried out by the partners' Tipping and Cueing Task Force, a Five Eyes effort to allow their intelligence-gathering systems to "provide real-time alerts of events of interest."
It notes terrorists continue to target airlines and hotels for attack, and that public Internet services in such facilities have "clear characteristics" — suggesting that could make it easier to find a suspect.
Edward Snowden, who once worked for CSEC's American counterpart, gave the document to Brazil-based journalist Glenn Greenwald, who collaborated with CBC. The public broadcaster released a censored version of the presentation, prepared by a CSEC "tradecraft developer" in the agency's network analysis centre.
Its disclosure prompted opposition MPs to accuse the Conservative government Friday of allowing CSEC to track Canadians and spy on them.
"Will the minister acknowledge that tracking the locations of Canadians by CSEC is against the law?" asked New Democrat MP David Christopherson in the House of Commons. "Will he at least acknowledge it is wrong?"
Defence Minister Rob Nicholson, who is responsible for CSEC, repeatedly told the House the eavesdropping service made it clear to CBC that Canadian communications were not targeted, collected or used, nor were travellers' movements being tracked.
CSEC spokeswoman Lauri Sullivan said in a statement that the agency is legally authorized to collect and analyze what is known as metadata — technical information used to route communications but not the actual contents of a phone call or message.
Some civil libertarians say CSEC's metadata monitoring is worrisome because even this material can reveal much about a person, such as their location and who they are contacting.
All CSEC activities "include measures to protect the privacy of Canadians," Sullivan said.
"The classified document in question is a technical presentation between specialists exploring mathematical models built on everyday scenarios to identify and locate foreign terrorist threats," she added.
"The unauthorized disclosure of tradecraft puts our techniques at risk of being less effective when addressing threats to Canada and Canadians."
The watchdog over CSEC, Quebec judge Jean-Pierre Plouffe, said in a statement Friday that he was aware of the metadata activities mentioned in the CBC story.
"The law prohibits CSEC from directing its activities at Canadians," he said. "In accordance with its mandate, CSEC is only allowed to use metadata to understand the global information infrastructure, for the purpose of providing intelligence on foreign entities located outside Canada and to protect computer systems of importance to the government of Canada."
Past commissioners have reviewed CSEC metadata activities, finding them to be in compliance with the law and to be subject to "comprehensive and satisfactory measures" to protect the privacy of Canadians, he added.
"CSEC is providing full co-operation to my office in the conduct of another ongoing in-depth review of these activities, which was formally approved in the fall of 2012."
Material disclosed by Snowden last year indicated that Canada helped the United States and Britain spy on participants at the London G20 summit in 2009. Other documents from Snowden's extensive cache suggested CSEC once monitored Brazil's department of mines and energy.
Earlier this week, interim federal privacy commissioner Chantal Bernier said CSEC should table an annual public report in Parliament describing its continuing activities.
Bernier also recommended the eavesdropping agency disclose annual statistics on cases in which it assists other federal agencies with requests for interception, which can include monitoring of Canadians.
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