SAN FRANCISCO : A pro-China propaganda campaign used fake social media accounts to try to stir up opposition, including protests, against mining firms that challenge China's business interests, U.S.-based cybersecurity firm Mandiant said on Tuesday. While politically motivated disinformation campaigns on social media have grown increasingly common, researchers say, such an operation targeting a specific industry of strategic importance to China is rare. The digital campaign, known to researchers as Dragonbridge, flooded Twitter and Facebook in recent months with posts raising environmental and health concerns over the operations of three major mining firms: Australia’s Lynas Rare Earths Ltd, Canada’s Appia…