Poke around the "properties" panels of Microsoft's Internet Explorer, and you're sure to run across IE's "content adviser."
"Ratings," the panel says, "help you control what kind of Internet content the users of your computer are allowed to view." Click another button, and you'll be able to set the amount of strong language, nudity, sexual content, and violence that your computer's users are allowed to see while they surf the Web.
Microsoft's content adviser is built on the PICS standard developed last year by Paul Resnick and James Miller at the World Wide Web Consortium. PICS, which stands for Platform for Internet Content Selection, is a general-purpose system for rating the content of Web pages. In their article, "PICS: Internet Access Controls Without Censorship," Resnick and Miller argue that technical solutions like PICS are what's needed to stem anti-Internet legislation like the Communications Decency Act. Because PICS lets parents program their computers not to display pornography to their children, they say, those same parents don't need to turn to lawmakers to keep the Internet safe for their children.
Resnick and Miller's argument is deeply flawed, but that doesn't really matter. PICS was readily seen by some companies as the antidote to the CDA. Microsoft adopted it, and now working PICS implementations are sitting on millions of desktops connected to the Internet.
The first thing to understand about PICS is that it's a framework for rating systems, not a rating system in itself. The RSACi rating framework that's distributed with IE allows you to rate sex, nudity, and so forth, but you can just as easily use PICS to rate the historical accuracy of a document, the amount of hate speech, or the political leanings of a document's author. Any of these rating systems can be described using the PICS rating service specification, stored in a file, and loaded into Internet Explorer.
Just for fun, I created the Simson Rating Service. This service tells you how much Simson there is in any document you might download. You can download the Simson service file and load it into Internet Explorer today! Try it.
Once you've created your own rating service, you need actual ratings as well. The PICS standard calls these ratings labels. Labels can be downloaded with a document, or they can be stored in a large database at another location. Labels can be invalidated automatically if the author of a document makes a change to it after the label is bestowed. And labels can be cryptographically signed, so they can't be forged.
Resnick and Miller have done a great job designing a framework for censorship. I don't think I could have done it better myself. They've designed a system that is technically strong, robust, and scalable. Documents can have multiple ratings, so the Simon Wiesenthal Center and the Imperial Knights of the KKK can both rate my homepage. And if some fundamentalist Christian group launches a gold-label rating service, they can issue those labels to sites for particular documents - resting assured the site won't underhandedly try to add information about evolution to a scholarly article on Genesis after earning an endorsement. Thanks to built-in safety measures, such a change would render the label invalid.
But the ideal behind PICS will be hard to attain. Internet Explorer implements the censorship controls, allowing parents to censor what their children can see, but Netscape Navigator doesn't. So a horny 14-year-old could either turn the controls off, or go download a more porn-friendly browser. And besides, most of the data on the Internet isn't rated, so it can't be filtered out.
The only way to make access controls effective is to implement them upstream from the end-user's PC, at the ISP or on an organization's firewall. That way users can't simply turn them off. An ISP, corporate MIS department or government technology officer could program their caching proxy servers to make a copy of every unrated document that's downloaded (along with the name of the person who downloaded it). Then the servers' administrators might review these documents at a later time and rate them according to their own beliefs, corporate policy, or government standard. If Johnny is looking at too much porn, or if Tan is pulling down documents that glorify democracy, somebody might just pay them a visit.
One of the greatest hopes of the Internet was that, in the process of opening up their countries to new commercial opportunities, totalitarian regimes would also open their people to new ideas. With PICS built in to their network infrastructures, repressive governments can selectively choose which information to let in and which to keep out.
Simply put, PICS could be the most effective global censorship technology ever designed.
