Comcast Corp.’s interference with Internet traffic has prompted a federal investigation and is at the center of calls for “Net Neutrality” laws, but another U.S. cable company appears to be doing the same thing without drawing scrutiny.

A study released Thursday found conclusive signs that file-sharing attempts by subscribers of Cox Communications were blocked, along with customers at Comcast and Singapore’s StarHub.

Of the 788 Comcast subscribers who participated in the study, 62 percent had their connections blocked. At Cox, 54 percent of subscribers examined were blocked, according to Krishna Gummadi at the Max Planck Institute for Software Systems in Saarbruecken, Germany. The institute examined the network connections of 8,175 Internet subscribers around the world.