The UK government has pressured ISPs to apply content filters to their customers’ connections, in the name of protecting children from unsuitable content. During 2014, ISPs will be approaching their customers and trying to persuade them to turn on filtering. But this is a mistaken approach arising from magical thinking — “this thing should exist so it must be possible”.

Content filters can’t work, for several reasons. Just a sample:

• For the most part they can be avoided. Techniques like using a freely-available VPN tool such as TunnelBear, or switching to non-ISP DNS allow users to effortlessly route round filters. As a consequence, relying on filters to do your parenting for you is foolish. Not only are they no substitute for parental oversight and care, they inculcate a careless reliance.
• They attempt to make objective a task which is subjective. For example, some people will regard web sites promoting gay rights or giving information about abortion as “unsuitable”, while others will treat both topics as essential resources for all. Who gets to decide for us all? The answer in most cases is “nobody knows”, since the ISPs are largely buying the blocking facility from third party suppliers rather than building it themselves. Statements by filtering advocates taking as read that there’s a consensus on what’s bad are deceptive.
• “Unsuitable” is subjective and will always fail most people. Worse, the third-party suppliers are likely to be conservative in their judgement, preferring to categorise something as a problem rather than risk letting something bad through. The term “overblocking” is used to describe cases where a web site is blocked by filters when there’s no good reason why it should be.

The government is proposing a “white list” of sites which should not ever be blocked, but this approach is flawed too; partly because their vision of which sites should be whitelisted only includes obvious, politically appealing cases like child welfare charities, omitting to mention harder cases such as mutual-support groups, political comment, satire and completely ignoring the sort of free speech cases that are politically unappealing to the government. Indeed, a comprehensive whitelist is probably impossible, because the internet is big (“Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is.”)

Even if a whitelist could work, most content providers won’t know they should be on it as blocking is invisible to them. Since the filter service is applied by ISPs to their customers’ connections as part of the service, they rely on customers raising the alert on overblocking. As a web page provider, I have no way to know whether a given ISP is actually blocking my site, and when I eventually find out there’s no deterministic way to get it fixed since neither the ISP nor their third-party provider have any duty to help me; in fact, the ISP’s contract with their supplier may actually prohibit them from helping me.

Most content providers might not even think to check anyway, even if there were a way to do so. Recently, the jQuery web site was added to the block list for UK ISP Sky after the domain was mistakenly listed in the “malware and phishing” category. This inexplicably broke many web sites, since over three-quarters of the top ten thousand web sites uses jquery.com hosted components. A church web site in Sheffield was blocked; my own company web site was blocked. The robots that do the ranking can unexpectedly take potshots at pretty much anything, and only the customers of the ISP involved could ever know.

Meanwhile, parents are lulled into a false sense of security. The Web is something of a mystery to many, and the assurance that “parental control filters” are keeping their children “safe” may well make the urgency of understanding how to supervise children on the Web lower. The correct path is sitting with children, assisting their use of technology, explaining how to decide who to trust, explaining when to ask for help or permission, applying discipline wisely.

If it was possible to magically determine the suitability of any random web site for any random web user, and if filtering could be made uncircumventable without destroying the utility of the Internet, maybe it would be OK to have a censorship switch that parents could flip. But none of that is possible, and the facilities we’re being sold will do more harm than good. You can help; check out blocked.org.uk or help fund the Open Rights Group video. That will help practically, and also fuel the political battle. After all, is the government ignorant of this, or is it just hypocritically demanding magic to defend itself from right-wing pressure?

(This article first appeared in the April 2014 issue of Linux Voice Magazine.  With apologies to The Verve for the title…)