U.S. National Security Agency whistleblower and international fugitive Edward Snowden told students at Upper Canada College that the mass collection of data by government spy agencies can get in the way of foiling terrorist plots.

Such programs can sometimes take resources away from targeted data collection of specific threats, Snowden told students at the private school in Toronto.

He spoke to the group via video conference from Moscow, where he currently resides. Snowden made his way to Russia after fleeing the U.S. and a brief stint living in Hong Kong.

"The problem with mass surveillance is when you collect everything, you understand nothing," he said during the video conference Monday evening.

Snowden, who exposed the NSA's domestic spying program in 2013, was the keynote speaker at the World Affairs Conference, which is co-organized by Upper Canada College, where he also took questions from students.

The title of the talk, which also included journalist Glenn Greenwald, was “Privacy vs. Security: A Discussion of Personal Privacy in the Digital Age.”

He told students that electronic spying programs constitute a threat to democracy and ought to be subject to more public debate about limits on how information is collected and used.

"This fundamentally changes the balance of power between the citizen and the state," he said.

Project Levitation

Snowden remains a controversial figure. The documents he leaked in 2013 revealed the U.S. government has programs in place to spy on almost everything that hundreds of millions of people do online, including emails, social networking posts, online chat histories, phone calls and texts.

Some of the documents revealed that other intelligence agencies, including the U.K.'s GCHQ, engage in the same kind of domestic spying.

Snowden mentioned the Levitation program, which sifts through millions of videos and documents downloaded online every day by people around the world, over the course of the 90-minute talk.

Details of the Communications Security Establishment project were revealed last week in a document obtained by Snowden and released to CBC News.

He also mentioned Canada's new anti-terror legislation that was introduced on Friday and includes a range of measures that would allow suspects to be detained based on less evidence and let CSIS actively interfere with suspects' travel plans and finances.

Snowden said it was important to be cautious when expanding such powers, particularly during what he called times of fear and panic.

"Once we let these powers get rolling, it’s very difficult to stop that boulder," he said.

Public Safety Minister Steven Blaney has said he believes the Security Intelligence Review Committee has the expertise to keep an eye on CSIS.

'Mother Teresa or Adolf Hitler'

Snowden went to Hong Kong and later Russia after illegally releasing documents that exposed widespread collection of citizens' phone and internet metadata by U.S. and other intelligence agencies.

Some have praised Snowden for exposing the breadth of government spying. Others feel his actions are treasonous.

Snowden told students that sometimes media coverage has focused too heavily on himself and not enough on the issues raised by the revelations of mass data collection.

"Whether or not I’m Mother Teresa or Adolf Hitler, that has bearing no whatsoever on the content of the reporting," he said.

Conor Healy, the student who arranged to have Snowden speak, said the decision prompted a fierce debate at his school.

"Our goal is to expose the student delegates to issues that are globally significant to them," Healy said Monday in an interview on CBC Radio's Metro Morning. "Snowden is undoubtedly one of the foremost perspectives on one side of an essential debate about our relationship with the government as it relates to personal privacy."