How often is this list updated? (Score 3, Informative)

To quote the article:

Fisher has so far instructed Internet providers with customers in the state to block subscribers from at least 423 Web sites around the world.

First, I find it hard to believe that there are only 423 web sites that offer kiddie porn, based soley on the amount of spam I get advertizing it. And in what way is this list updated? Porn sites move around constantly, and use any number of tricks to fool browsers ([e-mail] tricks, IP addresses instead of host names, etc.) so I think this list must be changing every few minutes. Do they reall y have someone sitting and watching as the porn sites get a new IP address?

I'm not saying anything for or against the block itself, I'm just saying this must be one hell of a headache to manange.