The Department of Homeland Security on Friday canceled a project to build a technology-based “virtual fence” across the Southwest border, saying that the effort  on which $1 billion has already been spent  was ineffective and too costly.

Janet Napolitano, the homeland security secretary, said she had decided to end the five-year-old project, known as SBI-Net, because it “does not meet current standards for viability and cost effectiveness.” In a statement, Ms. Napolitano said border agents would instead use less expensive technology that is already part of their surveillance equipment, tailoring it to the specific terrain where they will be scouting for illegal border crossers and drug traffickers.

Ms. Napolitano’s decision brought a long-expected close to a project carried out by the Boeing Corporation under a contract first signed in 2005 under President George W. Bush, which had been plagued by delays and cost overruns. Originally estimated to cost more than $7 billion to cover the 2,000-mile length of the border, it was the subject of more than a dozen scathing reports by the Government Accountability Office.

In a pilot program in Arizona, it cost about $1 billion to build the system across 53 miles of the state’s border. Officials said the new approach, using mobile surveillance systems and unmanned drones already in the Border Patrol’s arsenal, would cost less than $750 million to cover the remaining 323 miles of Arizona’s border.