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December 18, 2013 | Peter Bradwell








What happened?






It's not the first time this has happened




Why does it matter?


















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Comments (10)

  1. sigma:
    Dec 19, 2013 at 08:59 AM

    How were Sky mandated to block imgur in this case?

    There will be many more cases of over blocking and broken e-commerce before this runs its course.

  2. Martin:
    Dec 19, 2013 at 10:09 AM

    Very helpful to have the full story set out like this. As a TalkTalk-provided Wordpress account holder, it was very frustrating to have no access to my blog (which, although I don't use directly for business, is a potential way for clients to contact me), compounded by Wordpress' apparent inability to tell their users what was going on.

  3. Richard:
    Dec 19, 2013 at 11:21 AM

    Many thanks and I share Martin's concern over this issue. It least it's encouraging to know my suspicions of censorship voiced to WP on 26 July are now shown to have been correct and that you echo my ignored recommendations to WP engineers. I’d stressed to WP: “It's far too coincidental that this WP-ISP glitch is timed to accompany PM Cameron's declared war on I/net porn”. (I advised my readers accordingly at

    Generating over 370 exasperated comments from over 70 users in July and 275 from almost the same users indicates the size of this outrageous issue. It was especially aggravating this time round because WP had reported in July they were "taking steps to make sure we don’t see a repeat of this issue in the future"! I now understand their inability to have done so in these totally unacceptable situations.

  4. Stephen Blythe:
    Dec 20, 2013 at 02:02 AM

    I was one of the team members that were involved in responding to the enquiries from users about this issue.

    There was no warning, and it wasn't immediately clear what was causing people to have issues accessing their sites. Despite all of our best efforts, it initially could have seemed like there was an error on our side, because not all users were experiencing simple HTTP errors, but were having specific issues with access to various areas - mostly dashboards. Luckily, Westi (Peter) and others are sharp and clever enough to have pinpointed it to a specific ISP - but we still had no immediate fixes. TalkTalk denied it, and the IWF also said there should be no problems.

    Despite the steps we took to resolve the problem on our end, there was still no official word from the ISP days on; a totally unacceptable situation. Even now it's not entirely clear what was blocked - be it an IP range, a server, or what.

    There are serious questions that have to be asked about unilateral action like this from ISPs, and those originate from way before the proposed 'porn' filters. How exactly are ISPs implementing this IWF watch list, and why are we not challenging it more rigourously? There needs to be a massive increase in transparency to the way these issues are dealt with, and the response from TalkTalk is simply unacceptable.

    Disclaimer: I am an employee of Automattic, and member of the ORG Supporters' Council.

  5. Iain Collins:
    Dec 20, 2013 at 02:37 AM

    One reason why over blocking can go wrong is how the URLs are filtered. Typically routes are manipulated (via BGP) to force destinations to be routed through a filter. This happens on a per-IP basis (or for a range of IPs - the in case of large sites).

    This is the same approach ISPs and carriers have been using for a long time to null route bad hosts (like ones infected with viruses or caught spamming... even on rare occation to other organisations they just don't like).

    When URL's like WordPress or Imgur domains appear in lists things go wrong quickly because the systems which handle the blocking suddenly get flooded with HTTP requests.

    Most of these systems are typically very lightly taxed - people don't normally visit these sites and most popular sites are responsible and of course immediately take down inappropriate content immediately and never appear on the list.

    When they suddently have to start having ALL the customer network traffic for a popular destination they can't handle the load, either because they can't deal with handling so many HTTP requests per second, or because they can't cope with the sheer bandwith (e.g. some poor network interface somewhere doesn't have the capacity).

    As noted, while the details of the filtering systems vary widly - you could do DPI, or request proxying or something a bit in between those - they all tend to have the same weakness here, which is why it keeps happening at every provider.

    Note also the IWF maintain more than one list and not all ISPs choose to block all blacklisted URLs they publish.

    Source: Wrote the IWF filter used by Sky, have also worked on the HomeSafe front end at TalkTalk. Note: I am deliberately leaving out implmentation specific details here, but um yeah.

  6. sigma:
    Dec 20, 2013 at 09:38 AM

    Linkback to previous ORG article about TalkTalk's non opt-outable DPI of every browsing request of every TalkTalk user.

  7. James Sutherland:
    Dec 21, 2013 at 09:38 AM

    I think it's vital at this point that everyone affected - and their friends - switch ISPs, since this appears to have been TalkTalk's fault rather than the IWF's: call up, request your MAC (the reference number used to transfer to another ISP), and tell their customer service rep why you are changing. If they lose enough customers over it, perhaps TalkTalk will re-think their heavy-handed complacency over restricting services to customers.

  8. Ian Waring:
    Dec 23, 2013 at 08:06 PM

    I sounds like Talk Talk needed some education on how Content Delivery Networks work, and that if unwanted content is routed from them, that a better approach than blocking the CDN's Netblock is followed. I'm sure that's how imgur got cited recently, and given how Wordpress works (CDNs are a free bolt on to speed media delivery), I suspect the same root cause.

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