“No one is immune from such attacks," said Belyaiev. "In theory, a specialist with my level of expertise could plan and execute an operation to liquidate the first persons of any European state ... Pandora's box is open.”

“It is almost impossible to shoot it down," he said. "Only a net can help. And I predict that soon we will have to put up such nets above our cities, or at least government buildings, all over Europe.”