Espionage expert Calder Walton, author of "SPIES: The Epic Intelligence War Between East and West," warned President Donald Trump may be the most surveilled president in U.S. history due to his willingness to take calls from reporters and weak security at Mar-a-Lago. Trump's mobile phone number is widely known among Washington journalists, enabling direct calls for interviews. His accessibility exploits vulnerable foreign intelligence services. "One can only imagine how many foreign spies are also listening in to his phone conversations," Walton wrote. Mar-a-Lago has a history of security deficiencies; classified documents were reportedly found in Trump's bathroom during his first term.