The Center for Copyright Information (CCI) has announced that the United States Copyright Alert System (CAS), designed to combat online piracy, has been abandoned by its members after a four-year run.

The CAS was run by the CCI and involved voluntary participation by five ISPs -- AT&T, Verizon, Comcast, Time Warner Cable, and Cablevision -- which all agreed to send users a warning notice when requested by copyright owners represented by the Motion Picture Association of America (MPAA) or the Recording Industry Association of America (RIAA).

"After four years of extensive consumer education and engagement, the Copyright Alert System will conclude its work," the CCI said in a statement.

"The program demonstrated that real progress is possible when content creators, internet innovators, and consumer advocates come together in a collaborative and consensus-driven process. CAS succeeded in educating many people about the availability of legal content, as well as about issues associated with online infringement."

The CCI added that it remains committed to cooperating on preventing online copyright infringement through other measures, however.

Introduced in February 2013, the CAS was designed to dissuade piracy by sending alerts to users whose internet accounts had been used to download copyright infringing content, educating them on how to prevent this, and providing them with information on where to legally obtain the content.

Under the six-strikes system, the CAS allowed for users who received more than six alerts to have their speeds throttled temporarily by their ISP; their internet service tiers downgraded by their ISP; or be redirected to a landing page until their ISP was contacted or they completed an "online copyright education program".

At the end of 2015, ISP Comcast came under fire for displaying warnings on users' browsers accusing them of infringing copyright -- and tapping into their unencrypted browser sessions to do so.

The developer who discovered the Comcast warnings system said it could put users at risk, as the ISP was injecting code into users' browsers to conduct what amounted to a man-in-the-middle attack by intercepting the traffic between servers and users' devices.

"This probably means that Comcast is using [deep packet inspection] on subscribers' internet and/or proxying subscriber internet when they want to send messages to subscribers," developer Jarred Sumner said at the time.

"That would let Comcast modify unencrypted traffic in both directions.

"There are scarier scenarios where this could be used as a tool for censorship, surveillance, selling personal information."

For cases where a user had been incorrectly targeted by a warning notice, the CAS also developed an independent review system, run by the American Arbitration Association.

According to a report released in mid-2014, within a period of 10 months, 1.3 million copyright notices were sent to users: 722,820 first "educational" alerts; 214,654 second educational alerts; 165,065 third "acknowledgment" alerts; 94,599 fourth acknowledgment alerts; 60,477 fifth "mitigation" alerts; and 37,456 sixth mitigation alerts.

The Recording Industry Association of America at the time said the system was working, as demonstrated by a far lower number of people receiving six alerts than those receiving first alerts.

"Throughout the six 'stages' of the alert program, there were fewer and fewer alerts sent at each level," RIAA CEO Cary Sherman said in 2014.

"Does that all mean we can make a declaratory judgment that we've won the piracy fight? Of course not. This program was never intended to do that. But that CCI was finding fewer instances of piracy within the parameters of this program means that people were getting the message and going elsewhere for their music. 1.3 million alerts with no false positives is paradigmatic of an operationally sound system. We strived for accuracy and our goal was met."

Australia's similar three-strikes policy for online copyright infringement was shelved last year, after ISPs and rights holders were unable to reach an agreement on who should bear the costs of the regime.

Attorney-General George Brandis and Communications Minister cum Prime Minister Malcolm Turnbull had originally asked ISPs and rights holders to collaborate on creating a three-strikes policy in late 2014, which was released in the form of a draft code in 2015.

The Communications Alliance and Foxtel in April 2016 wrote to the Australian Communications and Media Authority (ACMA) saying, however, that the three-strikes policy should be abandoned, noting that over the past few months the copyright infringement battle has moved to the courts instead, where it was determined that rights holders should bear the cost of ISPs blocking access to foreign piracy websites.

Comms Alliance said the government should also pause to consider whether piracy is already being solved by streaming services.

In November, government research then predictably found that the availability of streaming services had in fact reduced online copyright infringement of TV shows, movies, music, and games "significantly".

The Consumer survey on Online Copyright Infringement 2016, conducted for the Australian Department of Communications, showed that once again, those who consumed both lawful and unlawful content spent more money than those who consumed all of their content legally.

Those downloading content illegally fell from 43 percent to 39 percent over the year, while those who streamed content legally rose from 54 percent to 57 percent. Those streaming TV shows rose increased from 34 percent to 38 percent; those streaming movies rose from 25 percent to 29 percent; and those streaming music fell from 29 percent to 26 percent.

Illegally downloaded movies dropped from 18 percent to 16 percent; music dropped from 29 percent to 26 percent; and TV from 19 percent to 17 percent.

"Rights holders' most powerful tool to combat online copyright infringement is making content accessible, timely, and affordable to consumers," Turnbull conceded in 2015 in response to the first report showing this trend.