How did the US stop spies in World War 1?

During World War I, the US utilized a combination of intelligence operations, counterintelligence efforts, and legal measures to stop spies. The Espionage Act of 1917 allowed for the prosecution of individuals engaging in espionage or promoting disloyalty, leading to arrests and convictions. The establishment of the Military Intelligence Division and collaboration with the Secret Service enhanced surveillance and infiltration of suspected spy networks. Additionally, public awareness campaigns encouraged citizens to report suspicious activities, thereby bolstering domestic vigilance against espionage.