Why are you baffled? Can you think of any category of crime where law enforcement succeeds in catching people 100% of the time? Of course not, because that is logistically impossible. Think about things like drinking and driving, using drugs, trafficking drugs, shop lifting, etc., etc. Lots of people get away with every type of crime every day.
And it really is not difficult for someone who is even a little bit technically savvy to get away with a whole range of online computer crimes indefinitely, including trading child porn.
Here are some of the things online criminals often do to both commit their crimes and to avoid detection:
War Driving: For those of you who are not familiar with this term, it consists of driving around in your car looking for open or poorly protected wireless networks that belong to other people. You can download a simple app for your smart phone that shows you all wireless networks in the vicinity and the type of encryption–or lack thereof. If you were to try this sometime, you would be amazed at how many people still don’t password protect their wireless networks. Moreover, even many password protected routers are using older encryption methods that are easily compromised using readily available hacking tools. And of course, if you log into someone else’s network, it is their IP address that shows up when law enforcement is scanning for IP addresses, not yours.
Public Proxy Servers: Proxy servers are servers that allow you to redirect all of your network traffic through someone else’s network, which, again, masks the IP address of the end user. There are many companies out there on the web that provide these services for a small fee and give you a broad range of servers to chose from in countries that still do not have child porn laws and that do not cooperate with law enforcement agencies in other countries. This one measure alone with defeat most law enforcement efforts to find the end user, and when combined with other measures, like war driving, the odds of getting caught become very slim.
Keep on the Move: Someone who uses other people’s networks and chooses a different network in a different place every time greatly reduces the risk that they will be detected.
Software Selection: Purchase online programs that encrypt all of your network traffic and hide your IP address. (These do exist.)
Untraceable Networks: Use something like the freely available Tor network that is virtually impossible to trace.
Use Common Sense: Here are some examples: Do not use public computers, family computers or any shared computer, for that matter. Use a single, small laptop that no one else uses and no one else knows about, and hide it some place where it will not be found. (This is not really hard to do.) Do not download illegal content to your phone and then carry that evidence around with you everywhere you go. (I see lots of people on the news getting caught this way!) Once open networks are identified, leave the cell phone at home when you use them. (Cell phones are exceptional tracking devices that enable law enforcement to trace your every step, including where you were at the time the crime was committed.)
This is only a partial list, but it gives you a good idea of some of the things that criminals can do to greatly reduce the odds of getting caught–and these measures apply to all sorts of crime, not just child porn. Nor is it difficult to find this type of information. With an hour or two of Googling, it’s actually pretty easy to find ways to get away with a whole host of cyber crimes. Even mainstream media is an excellent resource! (Most of what I have mentioned above are things I found in news articles.)
The fact of the matter is, most people who get caught get caught because they assume the odds of getting caught are low and don’t bothered to conceal their activities. But anyone who does take the level of risk seriously has a pretty good chance of getting away with their crimes. And sure, even very careful people are taking some risk and can get caught, but I suspect a lot of them never do.