The online review site Glassdoor Inc. launched nearly a decade ago and integral to its model was the ability for employees to leave an anonymous comments about their jobs. Ever since, the job recruiting company has fought efforts to release those identities, whether it be from a poorly reviewed employer or, now, from the federal government seeking potential witnesses in a criminal investigation.

The San Francisco-based company asked the U.S. Court of Appeals for the Ninth Circuit this month to block an attempt by federal prosecutors to unmask reviewers as part of a grand jury investigation. A federal court in Arizona ordered the company reveal identities of eight people who posted anonymous reviews about a federal contractor under investigation for fraud.