28/07/2013 18:52 BST | Updated 27/09/2013 06:12 BST

Why David Cameron's Internet Censorship Is a Terrifying and Terrible Idea


David Cameron's plan to introduce opt-out Internet censorship at service-provider level genuinely scares me. In an effort to crack down on child pornography and the number of children watching legal pornography, the PM has challenged service providers to automatically filter out porn and "sensitive subjects" unless customers specifically ask them not to.

What's more worrying is his treatment of the technical arguments against such a move: in his speech he said, "Set your greatest brains to work on this... You're the people who have worked out how to map almost every inch of the earth from space." Which is to say: "I don't want to talk about the problems or consequences. Just do it."

So, in plain English for the techno-phobic, here is why such a plan would be bound to fail, and more importantly would be harmful if it went ahead:

The censorship will block certain websites. Now, either a person decides which websites get blocked, or a computer decides. The Internet is far too big for a person to sort content into piles of "acceptable" or "not acceptable". According to YouTube's statistics page, 100 hours of video are uploaded to YouTube every minute. That's one website. It would take an army of people working around the clock centuries to censor the web, and every time a video was taken down it would pop up again on a dozen different sites. So the job would have to be outsourced to a computer, which can do it faster.

But computers are apocalyptically stupid. You could program one to, say, search videos for a certain percentage of exposed flesh and then block the ones that have anything over a magic number, but a computer can't tell the difference between a naked person in a pornographic video and a naked person in an art installation, or a medical textbook, or a political statement, or even some flesh coloured furniture. Computers only deal in yes or no, black or white, one or zero; they do syntax, not semantics. So the computer will be too strict and the flow of information will be disrupted. It will simultaneously be too lax - you see this with your spam email folder: the filter blocks emails with the word 'viagra' in so instead the spammers send emails about 'v1agra' and the computer lets them through.

Too many people, and apparently David Cameron is one of them, think that the Internet is a ineffable technological marvel like the monolith from 2001: A Space Odyssey, and that somewhere in a basement there are people in lab coats who have maps of it that look like diagrams of the London Underground. The Internet is no such thing: it's a botch built on a bungle built on a jury-rig.

For instance, IP addresses (which are a bit like a computer's online fingerprints: they identify it) used to have 32 digits. Why 32? Because the technician who came up with them thought that there would never be enough devices to need any more than a certain number of digital fingerprints and 32 just gave an arbitrarily huge number of possible combinations. The combinations ran out when the Internet exploded out of the gates like a greyhound on cocaine and now IP addresses have 128 numbers, but to stop those running out so fast you may find that all the devices in your house share one. What this illustrates is that you can't just change one part of the Internet without having serious consequences for the rest, and it's no good saying "You're clever: you figure it out."

But even if you could, it would still be a bad idea.

You decide what films are appropriate for you to watch. The box has guidelines and maybe they won't sell some to you if you're a child, but you have the final decision about whether you press play. Same for video games, same for books. You have the right to choose what media you consume. If this scheme goes ahead, you won't have that power anymore. You can opt out, but you shouldn't have to. That is not fair on the techno-phobic, who might not understand how to change the settings or will throw away the letter without reading it and then have their information censored by someone else because the default setting is the filter. And do you think that opting out will be anonymous, or do you suppose that a computer somewhere will quietly note the fact that you chose not to have your Internet, pornography and all, dissected? That won't look good; 'John Smith doesn't have filtered Internet: he must be a dirty bugger.' That's the sort of thing that could get blown out of proportion pretty easily and pretty nastily.

Cameron doesn't understand the Internet. Neither does Yvette Cooper, the shadow Home Secretary, who said he isn't being strict enough. The Internet has its ugly side: the spread of child pornography is a nasty, nasty problem that should be "stamped out", and yes, maybe the world would be a better place if we all watched a bit less porn. People do worry about what their kids watch online, but sitting them down and explaining that it's fantasy, that it can mislead and misdirect, will always be a better solution than outsourcing your parenting to your Internet service provider. Punishing innocent people by curtailing the information they want, especially perfectly ordinary information, can never be the answer. More to the point, it's a restriction of your right to choose what you watch. Some of the smaller providers have said they will not censor; if this awful scheme rolls out you should be thinking about switching to one of them.

UPDATE: It has emerged that TalkTalk, the UK's 4th biggest ISP, will be outsourcing their censorship to a Chinese company called Huawei using a system called 'Homesafe'. The system monitors all web traffic, whether customers opt out or not, but does not filter the content of those who opt out. i.e. your browsing is still monitored by the censor. Learn about it here.