People entering the United States to work or study receive visas allowing them to stay in the country for that purpose for a specific amount of time. However, some people don't voluntarily leave the United States once their visas expire. U.S. Immigration and Customs Enforcement takes the issue of those overstaying their visas quite seriously. ICE agents arrest people violating non-immigrant visas.
Possible Terrorism Threat
ICE considers certain visa violators as potential terrorism threats. While that's probably not the case with the majority of those overstaying a visa, it's a serious concern for the Department of Homeland Security. The department's Counterterrorism and Criminal Exploitation Unit works to prevent the exploitation of the U.S. Student and Exchange Visitor Program, which is part of the National Security Investigations Division, and manages the visa classifications of foreign students and their dependents on behalf of the Department of Homeland Security. Further, along with the U.S. Department of State, the SEVP monitors the schools that participating students attend as well as the students.
If you suspect immigration or visa irregularities, call ICE Hotline at 1-866-347-2423 to report the violations or visit the ICE website.