Before 2003, most administrative tasks related to US immigration were handled by the INS (the United States Immigration and Naturalization Service). After the attacks of September 11, 2001, in New York, the INS came under some criticism after it was revealed that many of the attackers were in the US on legal visas and had overstayed those visas. According to Time magazine, 13 out of the 19 attackers involved in the September 11 attacks entered the US on student, tourist, and business visas and overstayed their visas. In fact, Time reported that of the 7 million people entering the US on visas, about 3 million of them violated the terms of their visas by staying longer than authorized as of 2001.
The problem was worse because the INS had about 2000 enforcement agents in 2001 to monitor an estimated 6 million undocumented US citizens. Worse, many INS agents did not have access to federal crime databases and interaction between INS and law enforcement varied, so that information was not widely shared.
The INS was overseen by the US Justice department and its focus was naturalization and the services the average immigrant would need. Directly as a result of the 2001 attacks, the US immigration system received a major overhaul. A part of that overhaul resulted in the end of the INS. Instead, US immigration services were taken over by the USCIS (U.S. Citizenship and Immigration Services). The USCIS was created in March 2003 and even today the USCIS is part of the Department of Homeland Security (DHS). The link with the DHS ensures that part of the role is not just to offer immigration services but also to focus on security.
Separate agencies were created under the DHS to take care of immigration enforcement and border security. This ensured that the USCIS was free to focus on the administration of US immigration services while a much larger group of professionals could focus on any violations of immigrant laws in the US.
The creation of the USCIS also led to more information sharing and the creation of better databases about immigration. Now, law enforcement and immigration officials work together and share information to keep the US safe. As well, new rules under the USCIS ensure that there are stricter controls for immigrants. An immigrant must notify the USCIS about changes of address, for example, and employers and schools are required to keep information about immigrants on work and student visas to ensure that these visitors do not overstay their authorization or violate the terms of their visas.