Those visitors who fall under thenonimmigrant category must adhere to the National Security Entry-Exit Registration System (NSEERS) also known as Special Registration, put in place after September 11, 2002, to keep track of those entering and leaving our country in order to safeguard U.S. citizens and America’s borders. NSEERS was the first step taken by the Department of Justice and then by the Department of Homeland Security (DHS) in order to comply with the development of the Congressionally- mandated requirement for a comprehensive entry-exit program

Through the Special Registration system, the U.S. government can keep track of the more than 35 million nonimmigrant visitors who enter the United States as well as some nonimmigrant visitors already in the United States. These individuals are required to register with immigration authorities either at a port of entry or a designated ICE office in accordance with the special registration procedures.

Nonimmigrant alien visitors subject to NSEERS registration at the Port of Entry:

Certain citizens or nationals of Iran, Iraq, Libya, Sudan and Syria, as designated by the DHA Secretary in the Federal Reister.
Nonimmigrants who have been designated by the State Department.
Any other nonimmigrant, male or female regardless of nationality, identified by immigration officers at airports, seaports and land ports of entry in accordance with 8 CFR 264.1(f)(2).

For more information, please view: http://www.ice.gov/pi/specialregistration/