New York CNN — Corporations are scrambling to protect their senior executives as police warn of an elevated near-term threat against business leaders. Boards are reassessing security budgets. And CEOs are being told to delete their digital footprints. The stunning killing of UnitedHealthcare CEO Brian Thompson in Midtown Manhattan last week has shaken C-Suites across the country, forcing leaders to ask themselves uncomfortable questions about their own preparedness for a threat landscape that ap...