Not quite that simple

I won't go into the social side of this because I don't generally like joining the fuck police hype, but

There are various technical and legal reasons that child porn sites can still exist.

Let's say I want to run a website. If I'm an honest person running an honest website (plus the condition that this is a website I want people to know that I'm behind), I'm going to go to a webhosting company and I'll probably be giving them personal information when I pay (even if that personal information is just a paypal email address), and this hosting company is probably going to be located in the United States. Next I'm going to want (probably) a domain name. When I register a domain name I'm definitely giving up personal information. The difference now is that this information is publicly available, and you can find it for any website by doing a whois on the domain name (there are online tools to try this out if you want to play with it). So if I'm running a child porn site in this "honest" way anyone can get my home address just by doing a whois. But then there's the first way to get around thisthis is a pretty big issue on the Internet that anyone can get at personal information like this, so there are companies that will register a domain name in their name, and when you do a whois you see their information instead of the actual owner's. This company may or may not have your personal information, depending on their policy. So let's say the police can't get my information from a whois, they go to the hosting company (probably with a warrant) to get my personal information, and if for whatever reason they can't get it, they can still take the website down because the hosting company, being American, has to comply with American law and therefore can't host child porn (but they probably wouldn't get any charges unless they refused to take the child porn down).

But then where it gets more complicated is if I'm not hosting in the United States. The law enforcement of whatever country would need to pursue the matter, and this is more complicated because of the different meanings of child pornography in different regions. For example, lolicon (an anime style involving prepubescent girls often nude) is illegal in most western countries except (believe it or not) the United States.

But there's still more technologically that the police can do, but it starts to be bad policy, so naturally the United States is trying to do it. All traffic going from the United States to a foreign country needs to run on a cable from the United States to that country, as well as all traffic coming into the United States from a foreign country. This is then within the jurisdiction of the United States so they can put the technical means in place to filter trafficsuch as not allow traffic going to certain websites. This is what countries like China and Iran do, except they tend to block political websites instead of pornographic (but they might be doing some of that too). A few years ago Sweden was trying to pass a bill to allow the government (I'm not sure exactly which agency) to have full access without a warrant to all traffic going into and going out of Sweden (but not traffic that is staying within Sweden). This would be sort of like a customs of the Internet, except that people living anywhere could have traffic routed through Sweden without their knowledge even if they don't live in Sweden and aren't going to a Swedish website. Luckily, (I'm pretty sure) this bill did not pass.

Fortunately, the United States Naval Research department developed this nice little program called Tor, which (without going into the technical stuff), allows you to run a website that is impossible for anyone to figure out where the server running it is physically located or who is running it (anyone wanting to connect to it needs to install the Tor program though), and this is where you'll find most of the child pornography on the Internet. Because there is no known way to determine where files are being served from, it's impossible to prosecute anyone.