The U.S.-Mexico border spans nearly 2,000 miles, with only approximately 650 miles covered by a physical barrier. The rest of the border is enforced through a combination of manned patrol, surveillance towers, unmanned aircrafts (or drones) and other advanced technology — constituting a “virtual border.”Rather than the concrete wall that has become the cornerstone of U.S. Presidential candidate Donald Trump’s immigration rhetoric, it appears that the future of border enforcement will more likely be increased surveillance and use of technology. In 2015, the U.S. Customs and Border Protection began a biometrics trial in San Diego’s Otay Mesa port of entry. Biometrics refers to metrics related to human characteristics, like DNA, fingerprints, and facial recognition. In the Otay Mesa trial, biometric screening was used to monitor foreigners exiting by foot. This trial marked the first time the U.S. Customs and Border Enforcement used eye scans and facial recognition to monitor foreigners.In the future, the technology could be used to assure that foreigners who exit are the same that entered, monitoring those who overstay their visa and preventing the use of fake visas and identity theft.Biometric screening such as scans of fingerprints and facial images have long been part of U.S. government’s plan for border enforcement. However, new technology has been slow to be deployed due to the substantial financial burden it presents. A 2016 Pew Research Center study found that the number of unauthorized entries into the U.S. has remained steady since 2009, but the incoming number of immigrants from Mexico has steadily declined since 2007. Although Mexicans remain the majority of the United States' unauthorized immigrant population, the number of unauthorized Mexican immigrants has declined by about half a million since 2009. Meanwhile, the number of unauthorized immigrants from other regions — specifically Asia and Central America — has grown by over 300,000 since 2009.According to another Pew study from 2006, nearly half of unauthorized immigrants entered the U.S. with legal visas, but remained in the country after their visas had expired, which Pew has termed "overstayers." The physical wall would miss the large portion of immigrants who enter by legal means, requiring an increased use of technological systems that track immigrants beyond the border. The majority of the U.S. Customs and Border Protection’s current $447 million annual budget goes toward surveillance towers, unmanned aircrafts, retired military blimps, and other advanced technological equipment.Another border enforcement approach, announced in 2011 by U.S. Customs and Border and Customs, combines mobile surveillance, thermal imaging, and video technology, using sensors to detect individuals walking in the dark. General Dynamics, Lockheed Martin and Raytheon, the U.S.’s largest defense contractors, competed for the relevant contract but it was eventually given to Elbit Systems of America, the U.S. branch of the company that monitors Israel’s borders with Gaza and Egypt.These border enforcement strategies reflect more important moves towards surveillance and monitoring via technological advancements, rather than material barriers along the border.The shift to biopolitics, the governing of a population instead of a physical territory, is also influenced by the financial stakes defense contractors have in border enforcement strategies. While the U.S. public may be animated by visions of Trump’s concrete walls, future border enforcement will likely not look like Trump’s proposals.