The country is engaged in a long-term ideological struggle with radical Islam, Kenney told the annual Ottawa gathering hosted by the Conference of Defence Associations Institute.
"We need only to look to Copenhagen, to Paris, to Brussels and to Sydney," Kenney said.
"We need only consider the Toronto 18, the ongoing trials in Vancouver in the plot to bomb for the B.C. legislature and in Toronto against the alleged Via Rail bombers, to know that there is a high probability of future jihadists attacks from within."
The notion that western civilization and style of government are never going to be challenged is wrongheaded, he added.
"Some Canadians can be forgiven for indulging in that fantasy," Kenney said.
Canada's geographic remoteness, prosperity and pluralism "have given Canadians reason to think that we can avoid real threats to our peaceable dominion. Yet we face a global movement that quite literally defies reason."
Kenney, who took over from Rob Nicholson earlier this month, says the country "shouldn't overreact to this threat, nor should we underreact."
Debate over the federal government's proposed Bill C-51, which would increase the powers of security agencies, notably the Canadian Security Intelligence Service, began earlier this week in the House of Commons.
The concerns of the bill's critics are exaggerated, Kenney said. "We are taking all of these steps while respecting the rights of Canadians."
New Democrats oppose the legislation. The Liberals have said they will support it, but promise to fix some of the flaws if they form government after this year's election.
One of the loudest complaints about the bill is that it lacks additional oversight of intelligence services to prevent possible excesses. The government says no new mechanisms or bodies are needed beyond what already exists.
The director of the U.S. National Security Agency, which has been at the centre of an ongoing scandal for the depth and breadth of its eavesdropping, took to the podium Thursday to describe how Washington is now building in extra safeguards to cyber and surveillance regimes.
Admiral Mike Rogers said the leaks, precipitated by former contractor Edward Snowden, have led to a serious erosion of public trust, even though the NSA has broken no laws.
"Without trust we cannot deal with the many threats we are facing," he said. "It's a terrible place for us to be as a nation."
In the United States, they are just beginning a broad dialogue on how government and the private sector can collaborate to not only spot potential threats in cyberspace, but to also protect the privacy of citizens, Rogers said.
"What are we comfortable with? What are we not comfortable with?" he asked rhetorically.
"What is the level of oversight and control we'll have in place so that our citizens are comfortable with the idea of the exchange of information?"
Bill C-51 is the government's response to the killing last October of two Canadian soldiers, one of whom died during the Oct. 22 attack on Parliament Hill. The bill is meant to counter the threat of homegrown radicalism.
After his speech, Kenney was asked why he believes there will be more attacks even after C-51 is passed.
"The threat is going to keep mutating," Kenney said. "We have to be flexible in addressing the needs of our police and security agencies to counter the threat."
The speech also left little doubt that the Harper government intends to extend its current combat mission against the Islamic State of Iraq and the Levant when it comes up for renewal later at the end of next month.
Kenney said cabinet will soon consider proposals for the mission, as well as the question of whether the government has to go back to the House of Commons for approval.
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