Customers of Verizon Communications who pirate music files may soon receive an unwelcome letter from the company.

Verizon, the second-largest phone company in the United States, is expected to begin issuing "copyright notices" on behalf of the Recording Industry Association of America to those accused of illegally downloading songs from the Web, according to sources with knowledge of the agreement.

The sources, who asked for anonymity, said Verizon's letter campaign is part of a test, which is expected to begin on Thursday. Jonathan Lamy, an RIAA spokesman, confirmed the existence of the test but declined further comment.

The move is significant for the music industry because among Internet service providers, Verizon has typically been among the most reluctant to intervene in copyright cases on behalf of entertainment companies.

Full story: c|net