Muslims who change their names to sound more traditionally American, as immigrants have done for generations, or who adopt Arabic names as a sign of their faith are often investigated and catalogued in secret New York Police Department intelligence files, according to documents obtained by The Associated Press.

The NYPD monitors everyone in the city who changes his or her name, according to internal police documents and interviews. For those whose names sound Arabic or might be from Muslim countries, police run comprehensive background checks that include reviewing travel records, criminal histories, business licenses and immigration documents.

All this is recorded in police databases for supervisors, who review the names and select a handful of people for police to visit.

The program was conceived as a tripwire for police in the difficult hunt for homegrown terrorists, where there are no widely agreed upon warning signs. Like other NYPD intelligence programs created in the past decade, this one involved monitoring behavior protected by the First Amendment.

Since August, an Associated Press investigation has revealed a vast NYPD intelligence-collecting effort targeting Muslims following the terror attacks of September 2001. Police have conducted surveillance of entire Muslim neighborhoods, chronicling every aspect of daily life, including where people eat, pray and get their hair cut. Police infiltrated dozens of mosques and Muslim student groups and investigated hundreds more.

Monitoring name changes illustrates how the threat of terrorism now casts suspicion over what historically has been part of America’s story. For centuries, immigrants have Americanized their names in New York. The Roosevelts were once the van Rosenvelts. Fashion designer Ralph Lauren was born Ralph Lifshitz. Donald Trump’s grandfather changed the family name from Drumpf.

David Cohen, the NYPD’s intelligence chief, worried that would-be terrorists could use their new names to lie low in New York, current and former officials recalled. Reviewing name changes was intended to identify people who either Americanized their names or took Arabic names for the first time, said the officials, who insisted on anonymity because they were not authorized to discuss the program.

NYPD spokesman Paul Browne did not respond to messages left over two days asking about the legal justification for the program and whether it had identified any terrorists.

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