Major US internet service providers and music, movie and television industry associations have unveiled a long-awaited agreement aimed at curbing online copyright infringement.

The Copyright Alert System calls for ISPs to send a series of e-mail notices to internet subscribers whose accounts have been identified by content owners as illegally downloading music, movies or television shows.

After five notices, subscribers could be subject to “mitigation measures” by an ISP, including temporarily reducing their internet speed or redirecting their account to a landing page with information about copyright infringement.

The voluntary agreement does not oblige the ISPs to take punitive action, however, which they have been reluctant to do in the absence of a court order.

ISPs will not provide customers’ names to rights owners and subscribers can seek an “independent review,” at a cost of $35, to determine the validity of an infringement claim.

The Centre for Copyright Information, a new group founded by the ISPs and entertainment associations, stressed that the alert system “does not, in any circumstance, require the ISP to terminate an internet subscriber’s account.” But digital rights groups Public Knowledge and The Centre for Democracy & Technology (CDT) warned that it “lists internet account suspension among the possible remedies” to copyright infringement.

“Today’s agreement has the potential to be an important educational vehicle that will help reduce online copyright infringement,” Public Knowledge and the CDT said in a joint statement.