The University of Southern Californias Annenberg Innovation Lab studied which ad networks placed the most ads on sites accused of infringing music and film copyrights.
It issued a list of the top ten firms that placed Google at the second spot and Yahoo at the sixth place, CNET reports.
OpenX, a company based in Pasadena, Calif., that supplies digital and mobile advertising tools, was the top advertiser on pirate sites, the report said.
To help compile the list of the top infringing sites, USC used Google''s own Transparency Report, which lists the names of the sites that receive the most requests from copyright owners to remove infringing content.
According to the report, Google said that it hadn''t seen the report, but that it was a mistake to suggest the company''s ads are a major source of funds for pirate sites.
The firm pointed out that the complexity of online advertising has led some to conclude incorrectly that the mere presence of any Google code on a site means financial support from Google.