UK ISP Sky Broadband Removes Wrongful Imgur.com Website Block

The approach of attempting to restrict access to Internet piracy websites by employing dumb DNS or IP based blocks (censorship) claimed another victim over the weekend after customers of Sky Broadband (BSkyB) found that they could no longer access online image sharing website imgur.com, which had been wrongfully blocked by the ISP.

Most people should now be aware that all of the major broadband ISPs in the United Kingdom have, for the past year or so, been blocking Internet piracy websites following court orders. But the system is highly fallible and can be exploited by pirates to make life much harder for the ISPs.

During August 2013 Sky Broadband found itself in hot water after a piracy site, EZTV, managed to tweak its domain details so that Sky’s system ended up restricting access to a ton of legitimate sites including Facebook and TorrentFreak. An identical situation then hit the Radio Times, Crystal Palace FC and Taylor Swift’s official fan page among many others (here).

Now the same natural fallibility in this approach has struck again after the popular and quite legal imgur.com suddenly became inaccessible to millions of Sky’s customers. As before the situation stemmed from Sky Broadband’s attempt to block piracy site Yify-Torrents (here) but it didn’t stop there. Needless to say that the outcome resulted in a lot of angry complaints to Sky’s Twitter feed.

The problem occurred because Sky needs to keep the IP (Internet Protocol) addresses on its DNS (Domain Name System) servers up-to-date with similar data for their blocked sites (i.e. piracy sites often change their IP/DNS details so ISPs have to keep pace with that). But this approach is fallible because several legal websites and online servers can also share the same IP address (e.g. shared web hosting or cloud mirror servers etc.) and such addresses change hands all the time.

In the case of imgur.com it appears as if the site was blocked because YIFY began using CloudFlare’s servers in Australia, which function as an online Content Delivery Network (CDN) for live mirrors of website content (useful if the main website suffers an outage etc.).

As a result of insufficient checking, which is likely to occur when ISPs start to rely too much upon automation (i.e. the more sites you block the harder they become to correctly monitor), Sky ended up sticking CloudFlare’s IP on its block list and that also blocked imgur.com as they use the same service (we suspect that other sites might have been similarly affected).

The incorrect block has now been lifted but this is unlikely to be the last such mistake as the same fallibility exists for all providers, although such errors only tend to make the headlines when popular websites are impacted.