"Sunni Islamist radicalization leading to violence is a serious threat to both Canada and its allies," says CSIS in a heavily censored February 2012 assessment released through an Access to Information request.
The assessment also finds that "a large number of venues have been, and continue to be, used to further Islamist extremist ideology" in Canada.
While the RCMP has connected places like the Salaheddin Islamic Centre in Toronto to efforts to indoctrinate people in extremist Muslim ideology, CSIS finds radicals are created through other venues too.
Its report finds that husbands, wives and siblings push each other into extremist thinking, while others are drawn into support of Islamist violence through chat rooms on jihadi websites or in Canadian prisons.
In other cases, CSIS finds Islamists are immigrating to Canada.
"On occasion, the radicalization process appears to take place largely outside Canada, either prior to the extremists' arrival in our country or after a conscious decision to leave Canada," says the spy service.
CSIS doesn't expect the problem to go away soon.
"The Service assesses that radicalization will continue to develop in the foreseeable future in Canada," its report says.
A CSIS spokeswoman say Canadians should be aware of genuine dangers.
"Canada has been identified as a legitimate target by various individuals who espouse the ideology of Al Qaeda, and has not been immune from the more recent phenomenon of 'home-grown' terrorism," said Tahera Mufti in an e-mail.