A new copyright alert system has begun rolling out this week in the United States in an effort to curb online piracy.
The system, informally known as six strikes, is a voluntary effort of the music and film industries, with the largest Internet service providers participating.
The program will use warnings and could result in slowed or suspended Internet connections, but users will not lose Web access entirely. Still, some civil liberties groups and Internet activists call it too invasive and warn it could unfairly penalize some users.
It is being coordinated by the Center for Copyright Information, created by the music and cinema industries and the five largest broadband Internet firms.
"We hope this cooperative, multi-stakeholder approach will serve as a model for addressing important issues facing all who participate in the digital entertainment ecosystem," said Jill Lesser, executive director of the center.
Lesser said the program is "meant to educate rather than punish, and direct (consumers) to legal alternatives."
She added that people who believe they get warnings in error will have an easy to use process to appeal, and get an independent review.
Despite the six strikes moniker, backers of the system say it is not intended to cut off Internet access for copyright infringers, who will get up to six warnings.
The steps announced by the big Internet firms include pop-ups, which force users to acknowledge warnings, and mechanisms to slow a user's access to near-dialup speeds.
Some critics say that redirecting users is equivalent to a browser hijack while others say innocent users may be snared by the system.
"It's an elaborate surveillance system," said Corynne McSherry at the Electronic Frontier Foundation, a digital rights group.
"There will be innocent people caught up in this system, it's inevitable."
McSherry said another problem is a lack of transparency in the system, which is private and cannot be challenged in the same way as a law.
"We have an elaborate private enforcement system for copyright, because they weren't happy with what they could get from Congress," she said.
Internet subscribers "face consequences based on nothing more than an accusation," McSherry said.
Other activists were even more blunt in their criticism.
"Soon your ISP will be spying on you and messing with your internet at Hollywood's request," said a tweet from the online activist group Fight for the Future.
The group said that under new system, "they can slow down or shut off your internet connection without any due process, claiming copyright infringement."
But the Information Technology and Innovation Foundation, a Washington think tank, called the program "a model for addressing digital property rights without unduly inhibiting Internet use and innovation."
Participating in the program are the five largest broadband Internet providers -- Comcast, Time Warner Cable, AT&T, Cablevision and Verizon -- covering some 85 percent of US residential customers.
The firms this week began releasing details of their enforcement.
Comcast said on its website its "progressive alerts will start out as informational and then evolve into 'mitigation alerts'" which require customers to call the company, but that the program will not involve "termination."
Verizon said it will implement "temporary Internet speed reductions of two or three days for customers who receive at least five alerts."
Cablevision said it "may temporarily suspend your Internet access for a set period of time" for repeat violators.
AT&T said customers would "be required to take an extra step to review materials on an online portal that will educate them on the distribution of copyrighted content online" but also stressed its privacy protections.
AT&T vice president Ben Olson added that even though its measures are voluntary, "many customers will respond positively when first notified and will not need additional reminders."