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.

Philadelphia-based Comcast is the country's second-largest Internet service provider, with 14.1 million subscribers. Atlanta-based Cox Communications is the fourth-largest, with 3.8 million. It is part of privately held Cox Enterprises Inc.