Companies have long used criminal background checks, credit reports and even searches on Google and LinkedIn to probe the previous lives of prospective employees. Now, some companies are requiring job candidates to also pass a social media background check.

A year-old start-up, Social Intelligence, scrapes the Internet for everything prospective employees may have said or done online in the past seven years.

Then it assembles a dossier with examples of professional honors and charitable work, along with negative information that meets specific criteria: online evidence of racist remarks; references to drugs; sexually explicit photos, text messages or videos; flagrant displays of weapons or bombs and clearly identifiable violent activity.

“We are not detectives,” said Max Drucker, chief executive of the company, which is based in Santa Barbara, Calif. “All we assemble is what is publicly available on the Internet today.”

The Federal Trade Commission, after initially raising concerns last fall about Social Intelligence’s business, determined the company is in compliance with the Fair Credit Reporting Act, but the service still alarms privacy advocates who say that it invites employers to look at information that may not be relevant to job performance.

And what relevant unflattering information has led to job offers being withdrawn or not made? Mr. Drucker said that one prospective employee was found using Craigslist to look for OxyContin. A woman posing naked in photos she put up on an image-sharing site didn’t get the job offer she was seeking at a hospital.

Other background reports have turned up examples of people making anti-Semitic comments and racist remarks, he said. Then there was the job applicant who belonged to a Facebook group, “This Is America. I Shouldn’t Have to Press 1 for English.” This raises a question. “Does that mean you don’t like people who don’t speak English?” asked Mr. Drucker rhetorically.

Mr. Drucker said...