The requests, which the F.B.I. says are critical to its counterterrorism efforts, have raised privacy concerns for years but have been associated mainly with tech companies. Now, records show how far beyond Silicon Valley the practice extends — encompassing scores of banks, credit agencies, cellphone carriers and even universities.

The demands can scoop up a variety of information, including usernames, locations, IP addresses and records of purchases. They don't require a judge's approval and usually come with a gag order, leaving them shrouded in secrecy. Fewer than 20 entities, most of them tech companies, have ever revealed that they've received the subpoenas, known as national security letters.