It has been revealed today that Cameron is planning on ordering Internet Service Providers to block “extremist” websites.

It may surprise some people, but I don’t have a problem with this. The reason I’m not worried is that it’s not going to work, because Cameron wants to use the anti-Child-Abuse Cleanfeed system to do it. One of the many criticisms of Cleanfeed is that it’s completely ineffective in the face of either a web site host or an end user with even a hint of technical ability, and there are even US Navy-sponsored initiatives to help users in oppressive regimes get around blocks.

The counter-argument by Cleanfeed is that it is not designed to stop “determined access”, just inadvertent access to unwelcome images. So it would seem the new system will prevent inadvertent access to terrorist and extremist web sites, not something that will likely have any significant access besides a few “Tough on terrorism” headlines in the Daily Mail.

What I do have a problem with is the slippery slope. When Cleanfeed was first introduced, many assurances were given that it would only be used to block images of child abuse. We’ve already seen that go wrong with the accidental block of Wikipedia, and it appears the secret list will now be extended to content someone, somewhere deems “extremist”. First it will be the obvious targets, but what about websites calling for civil disobedience or protest? The police will no doubt have some input into the block list and do you think they will be able to resist the temptation to add sites causing them headaches?

Mysteriously, they will become inaccessible with no way of verifying if you are on the list and no appeal.

This is worrying when it happens to mainstream websites, because Cleanfeed is somewhat dishonest and doesn’t tell you that you have hit a blocked site. Instead, you receive a generic File-not-found message. Not being a terrorist, why would you bother installing any mechanism to work around the blocks? No doubt people will figure out they have been blocked eventually, but in the case of a time-critical demonstration the damage could already have been done.

And once it is in place, might the powers that be try even more desperately to find ways of closing the loopholes in the system? I doubt this would work, given even China has failed in this regard so far, but there is a huge amount of collateral damage that could happen if they tried.

No doubt Cameron will say he doesn’t want to do any of the above, but will there be sufficient safeguards put in place? We saw when David Miranda was stopped at an Airport, where supposed anti-Terrorism powers were abused due to a lack of appropriate rules and oversight, that such things are critical. And what prevents a future, less liberally minded, parliament from quietly chipping away at those safeguards once the system is operational. Being a secret system, how would the public know?

If Cameron wants to do this, he needs to propose a better way than Cleanfeed. A more transparent system, with judicial oversight. And then we can talk.