OTTAWA—The head of the Canadian Security Intelligence Service warns that China is undermining Canada through its efforts to steal valuable technology and silence critics of Beijing’s policies. In a speech Tuesday sponsored by the Centre for International Governance Innovation, CSIS director David Vigneault said all sectors of Canadian society must work together to fend off these threats. “To be clear, the threat does not come from the Chinese people, but rather from the government of China that is pursuing a strategy for geopolitical advantage on all fronts—economic, technological, political, and military,” Vigneault said. He bluntly stated that Beijing is “using all events, all elements of state power, to carry out activities that are a direct threat to our national security and sovereignty.” “We all must strengthen our defences.” Vigneault says ill-intentioned countries will aim to “take advantage” of Canada as it works to get back on its economic feet once …