The Trump administration has increased the number of students and academics it is seeking to deport in recent days, a new front in its efforts to restrict immigration. About 800 international students have been stripped of their visas, according to universities and media reports. In late March, Secretary of State Marco Rubio told reporters that the administration was revoking visas daily. The White House has asserted that some of these immigrants threaten national security, though some legal experts have said the administration is trampling free speech rights. In the vast majority of cases, however, immigration officials have not provided reasons. The identities of most of the students have not been publicized. Some immigration lawyers said it appeared that many were pursued because they had broken laws, such as by driving under the influence.Here is what we know about the students the Trump administration is seeking to deport. Who is being targeted? The affected students are, for the most part, in the United States with visas that allow foreign nationals to enter for full-time study. A handful have green cards, making them lawful permanent residents. These students attend schools across the country, both private and public, including Arizona State University, the University of California and New York University. While some students have been involved in pro-Palestinian activism, it appears a majority are not. Some of the visa revocations seem to be related to legal infractions in the students’ past. “This is totally unprecedented,” said Fuji Whittenburg, an immigration lawyer in Calabasas, Calif., who is representing some of the students. She added, “A brush with law enforcement that didn’t necessarily result in an arrest or a conviction is all it took.” Ms. Whittenburg said that one of her clients got a D.U.I. while studying in the United States more than a decade ago. When he applied for a second visa more recently, he disclosed the charge to U.S. consular authorities and was ultimately approved to pursue further studies. Editors’ Picks What a New American Citizen Learned on Route 66 Simple Sandals Are Always a Good Investment Is ‘Reef Safe’ Sunscreen Really Better? This month, that visa was suddenly revoked.