The Washington Post reports:

Some of the nation's largest Internet service providers have agreed to block connections to newsgroups and Web sites that offer child pornography, according to an announcement today by the New York State Attorney General's Office.

The move follows an eight-month child pornography investigation. The probe turned up 88 newsgroups involving 11,390 sexually lewd photos featuring prepubescent children. Among them were photos of children being raped and sexual activity involving animals, according to state Attorney General Andrew M. Cuomo.

The announcement over at the New York AG's website adds some details:

[T]he Attorney General's office developed a new system for identifying online content that contains child pornography. Every online picture has a unique "Hash Value" that, once identified and collected, can be used to digitally match the same image anywhere else it is distributed. By building a library of the Hash Values for images identified as being child pornography, the Attorney General's investigators were able to filter through tens of thousands of online files at a time, speedily identifying which Internet Service Providers were providing access to child pornography images.

In addition to eliminating the Newsgroups, the ISPs have also agreed to purge their servers of all child pornography websites identified by the National Center for Missing & Exploited Children ("NCMEC"). NCMEC regularly reviews and updates its registry of these illegal sites to ensure the list reflects the current presence of such websites on the Internet.

  When Pennsylvania tried to do something somewhat similar -- albeit with court orders rather than a voluntary agreement -- Pennsylvania's effort was struck down as unconstitutional. I blogged about Pennsylvania law here in 2003, and the law was invalidated in CDT v. Pappert, 337 F. Supp.2d 606 (E.D. Pa. 2004).

  New York's effort is different in that the state has reached an agreement with the ISPs; the ISPs have agreed to "voluntarily" block the connections rather than be forced to do so. Off the top of my head, I don't know whether customers of these ISPs could still challenge the agreement on some of the constitutional grounds raised in the Pennsylvania case. I would think not, but I don't know.