IT knows who you are. It knows where you live. It knows what you do.

It peers deeper into American life than the F.B.I. or the I.R.S., or those prying digital eyes at Facebook and Google. If you are an American adult, the odds are that it knows things like your age, race, sex, weight, height, marital status, education level, politics, buying habits, household health worries, vacation dreams — and on and on.

Right now in Conway, Ark., north of Little Rock, more than 23,000 computer servers are collecting, collating and analyzing consumer data for a company that, unlike Silicon Valley’s marquee names, rarely makes headlines. It’s called the Acxiom Corporation, and it’s the quiet giant of a multibillion-dollar industry known as database marketing.

Few consumers have ever heard of Acxiom. But analysts say it has amassed the world’s largest commercial database on consumers — and that it wants to know much, much more. Its servers process more than 50 trillion data “transactions” a year. Company executives have said its database contains information about 500 million active consumers worldwide, with about 1,500 data points per person. That includes a majority of adults in the United States.

Such large-scale data mining and analytics — based on information available in public records, consumer surveys and the like — are perfectly legal. Acxiom’s customers have included big banks like Wells Fargo and HSBC, investment services like E*Trade, automakers like Toyota and Ford, department stores like Macy’s — just about any major company looking for insight into its customers.

For Acxiom, based in Little Rock, the setup is lucrative. It posted profit of $77.26 million in its latest fiscal year, on sales of $1.13 billion.

But such profits carry a cost for consumers. Federal authorities say current laws may not be equipped to handle the rapid expansion of an industry whose players often collect and sell sensitive financial and health information yet are nearly invisible to the public. In essence, it’s as if the ore of our data-driven lives were being mined, refined and sold to the highest bidder, usually without our knowledge — by companies that most people rarely even know exist.

Julie Brill, a member of the Federal Trade Commission, says she would like data brokers in general to tell the public about the data they collect, how they collect it, whom they share it with and how it is used. “If someone is listed as diabetic or pregnant, what is happening with this information? Where is the information going?” she asks. “We need to figure out what the rules should be as a society.”