SAN FRANCISCO — Here's another reason for ailing newspaper and magazine publishers to wince: On average, the audience perusing unauthorized online copies of their articles is nearly 2.5 times larger than the readership on their own websites, according to a study being released Thursday.

However, the problem, flagged by copyright cop Attributor Corp., could turn into a golden opportunity if media companies figure out a way to mine advertising revenue from the traffic flocking to their pirated stories posted on blogs and other sites.

Attributor, which makes software that trolls the Internet for copyright violations, estimates the average Web publisher could collect more than $150,000 in additional revenue by selling ads alongside its unlicensed material.

It's an unscientific estimate, based on an assumption that advertisers would pay $1 for every 1,000 pages of unauthorized material viewed on Web sites that aren't owned by the copyright owners.

If anything, Attributor believes its calculations understate the opportunity for fleeced publishers. The Redwood City-based company already is working with a few media companies that could generate more than $1 million in annual advertising by enforcing their online copyrights, said Rich Pearson, Attributor's vice president of marketing.

"The people creating all this content are not being justly rewarded and publishers are clamoring for every dollar of revenue that they can get in this environment," Pearson said.

There's a whiff of self-interest in Attributor's findings. The privately held company stands to profit if it can persuade potential customers that the Internet is riddled with copyright abuses that could translate into more revenue if the poachers are identified. Attributor's current customers include The Associated Press, Reuters and The Financial Times.

But the issue of copyright infringement was a sore point for media executives long before Attributor began developing its detection system in 2006.

In the most extreme cases, the copyright backlash has triggered bitter legal battles like the one that culminated in the demise of the music sharing service Napster. In a showdown still unfolding, Viacom Inc. is suing Internet search leader Google Inc. for alleged copyright infringement on its video-sharing site, YouTube.

The worst copyright headaches diagnosed in Attributor's study occurred in stories about automobiles, travel and movie reviews. The readership of unlicensed stories in those three categories was four to seven times higher than on the websites where the content originated.

Even if they can extract more money from the unauthorized use of their content, newspaper and magazine publishers seem unlikely to recover the revenue that has evaporated as more advertisers shifted their spending to the Internet during the past five years.

That's because Internet ads generally cost a fraction of print ads -- a dichotomy that has caused newspapers to lay off thousands of workers to offset double-digit percentage declines in their revenues.

Attributor's study, conducted from Sept. 12 through Oct. 12, reviewed 30 billion Web pages hosting copies of stories from more than 100 major websites. None of the sites belonged to Attributor's current customers. After excluding all properly licensed content, Attributor then discarded any page that copied less than 50 per cent or fewer than 125 words of a copyrighted story.