BOSTON (AP) — A new report by a public-private task force including Microsoft, Amazon, the National Governors Association, the FBI and Britain’s and Canada’s elite crime agencies offers a comprehensive plan for assaulting ransomware. Homeland Security Secretary Alejandro Mayorkas is set to join the formal online launch Thursday. But the challenge is daunting. The task force acknowledges there’s no silver bullet for a scourge whose perpetrators enjoy safe harbor abroad. The criminal syndicates that dominate the ransomware business are mostly Russian-speaking and operate with near impunity out of Russia and allied countries. The U.S. government deems ransomware a national security threat.