Censoring a little is hard. Censoring a lot is easy.

Update: IWF has stopped blocking Wikipedia. Their reasoning here. An interesting sentence from their release: “We regret the unintended consequences for Wikipedia and its users.”

Tech blogs in the UK and US are reporting that users of six British ISPs are being prevented from editing Wikipedia. Looking at why this is the case offers some revealing insights about just how dificult it is to censor the Internet without breaking important pieces of it.

Several British ISPs – representing the vast majority of UK web users – subscribe to a service from a group called the Internet Watch Foundation, a group which describes itself as “The UK Hotline for reporting illegal content specifically: Child sexual abuse content hosted worldwide and criminally obscene and incitement to racial hatred content hosted in the UK.” The service blocks access to URLs that IWF has investigated and determined contain child pornography, and routes traffic to those URLs through a transparent proxy, blocking access to the offending URL. A page on Wikipedia on the rock album “Virgin Killer” by the Scorpions has flagged by the IWF and now UK users who attempt to access that page receive a 404 error. IWF explains the block:

A Wikipedia web page, was reported through the IWF’s online reporting mechanism in December 2008. As with all child sexual abuse reports received by our Hotline analysts, the image was assessed according to the UK Sentencing Guidelines Council (page 109). The content was considered to be a potentially illegal indecent image of a child under the age of 18, but hosted outside the UK. The IWF does not issue takedown notices to ISPs or hosting companies outside the UK, but we did advise one of our partner Hotlines abroad and our law enforcement partner agency of our assessment. The specific URL (individual webpage) was then added to the list provided to ISPs and other companies in the online sector to protect their customers from inadvertent exposure to a potentially illegal indecent image of a child.

The image in question is the controversial album cover for the record – it depicts a naked pre-pubescent girl, her genitals obscured. The record was released under a different cover in several nations to avoid controversy, and some members of the Scorpions have distanced themselves from the cover art, blaming the record company, RCA, for the decision. Whatever your feelings about the cover, it’s not hard to find online. A Google Image search on google.co.uk for “virgin killer” (with safe search off) turns up the album cover, both censored and uncensored. (It will be interesting to see whether IWF attempts to block this search on Google as well.)

If that were the whole story, there probably wouldn’t be much discussion about this subject. But the way in which IWF blocks content has triggered an interesting “immune response” from Wikipedia, blocking many Britons from editing Wikipedia. From what I can tell about the IWF system from online accounts, IWF subscribers are sent lists of possibly offending URLs, and instructed to set their routers to direct traffic through a proxy when they encounter requests for these URLs. These proxies (I’m unsure if they’re run by the ISPs or by IWF) then block access to specific URLs – i.e., the URL for the Wikipedia page for Virgin Killer.

If UK ISPs were routing requests for “http://en.wikipedia.org/wiki/Virgin_Killer” through a transparent proxy, that wouldn’t be a major problem. But reports suggest that they’re routing all wikipedia.org URL requests through the proxy, letting 99.99% through and blocking the Virgin Killer requests at the proxy level. This is a problem – the millions of requests for Wikipedia pages are now coming from just a couple of IP addresses, one per ISP. Wikipedia is very sensitive to edits made through proxies – they’re often used to post spam to the site. If a single spammer posts from one of these proxy IPs, everyone using that IP will be banned from editing. By blocking access to a single article, IWF has functionally prevented most Britons from contributing to Wikipedia.

This is almost certainly not what either Wikipedia or IWF was attempting to achieve, but it’s got the interesting affect of alerting millions of Britons to the existence of IWF and their role, even if only a few hundred would have missed being able to access this single Wikipedia page. This happens with almost all online censorship – censors end up blocking more than they wanted to, and they make a larger group of users aware that censorship is taking place. Few Turks are searching YouTube for content defaming Ataturk… but when Turkey blocks the whole site to Turkish viewers to block access to those videos, viewers ask why they can’t look at the video of the cute cat flushing the toilet. Millions of viewers who had no interest in an act of online activism end up paying attention because censors blocked more than they could have. (I’ve written at some length about this idea in my Cute Cat Theory posts.)

So why don’t censors just block individual URLs? In some cases, they’re simply not very sophisticated and they overblock because they don’t know any better. Sometimes they overblock as a way of putting pressure on the web host – if Google sees that all Turks can’t access YouTube, perhaps they’ll choose to take down the offensive videos on their own. I doubt that’s what’s going on here… but perhaps Wikipedia will let us know whether they’re in conversations with IWF about removing the image.

In the meantime, IWF could solve the problem by instructing routers to proxy requests for “*.wikipedia.org/wiki/Virgin_Killer*” rather than proxying all wikipedia.org URLs. (This assumes that I’m right about how their proxy works, which I may not be.) Or they could use the X-Forwarded-From header, which the Register suggests as a workaround. Wikipedia, of course, could either remove the image or allow the blocked British IPs to resume editing – I predict neither of those courses of action will transpire. (And of course, I’m speaking as my own opinionated self, not in any official role as a Wikimedia Foundation advisor.) Should be interesting to watch this one play out.