The United States government is increasingly using social media to investigate people who may represent a security threat to the country. The latest example comes from the Department of Homeland Security’s Customs and Border Protection office. It wants to ask foreign visitors to provide information about their accounts on social media sites like Facebook and Twitter. An optional or non-required question would be added to the form that people must complete before entering the United States. The form asks information like the person’s name, phone number, and countries they have visited since 2011. The proposed social media question would only concern travelers who do not need a visa to enter the United States. Travelers from 38 countries are permitted to enter the U.S. without a visa. The Customs and Border Protection office said in its proposal that adding the question would affect about 24 million people.