The blockade of the Pirate Bay by UK ISPs is causing trouble for CloudFlare customers. Several websites have been inadvertently blocked by Sky because a Pirate Bay proxy is hosted behind the same IP-addresses. In a response, CloudFlare threatened to disconnect the proxy site from its network.

Like any form of censorship web blockades can sometime lead to overblocking, targeting perfectly legitimate websites by mistake.

This is also happening in the UK where Sky’s blocking technology is inadvertently blocking sites that have nothing to do with piracy.

In addition to blocking domain names, Sky also blocks IP-addresses. This allows the site to stop https connections to The Pirate Bay and its proxies, but when IP-addresses are shared with random other sites they’re blocked too.

This is happening to various customers of the CDN service CloudFlare, which is used by many sites on the UK blocklist. Every now and then this causes legitimate sites to be blocked, such as CloudFlare customers who shared an IP-address with Pirate Bay proxy ilikerainbows.co.uk.

Although the domain is merely a redirect to ilikerainbows.co, it’s listed in Sky’s blocking system along with several CloudFlare IP-addresses. Recently, the CDN service received complaints from users about the issue and alerted the proxy owner.

“It has come to our attention that your website — ilikerainbows.co.uk — is causing CloudFlare IPs to be blocked by SkyB, an ISP located in the UK. This is impacting other CloudFlare customers,” CloudFlare wrote.

The CDN service asked the proxy site to resolve the matter with Sky, or else it would remove the site from the network after 24 hours.

“If this issue does not get resolved with SkyB though we will need to route your domain off CloudFlare’s network as it is currently impacting other CloudFlare customers due to these blocked IP addresses.”

The operator of the “Rainbows” TPB proxy was surprised by Sky’s overbroad blocking techniques, but also by CloudFlare’s response. Would CloudFlare also kick out sites that are blocked in other countries where censorship is common?

“What do they do when Russia starts blocking sites under their system? Are they going to kick users off CloudFlare because there’s a Putin meme that the Russians don’t like?” Rainbows’ operator tells TF.

Instead of waiting for the domain to be switched off by CloudFlare he reverted it back to the domain registrar’s forwarding services. The main .co domain still uses CloudFlare’s services though, as does the official Pirate Bay site.

This is not the first time that CloudFlare customers have been blocked by mistake. Earlier this year the same thing happened to sites that shared an IP-address with The Pirate Bay. At the time we contacted Sky, who informed us that they do all they can to limit collateral damage.

“We have a process in place to monitor requested site blocks to limit the chances of inadvertently blocking sites, and in addition to this if we are advised by a site owner or Sky customer that a site is being inadvertently blocked we take the necessary steps to remove any unintended blocks,” a Sky spokeswoman said.

In addition to Sky we also contacted CloudFlare about the issue multiple times this year, but the company has yet to reply to our inquiries.

It’s clear though that despite cheers from copyright holders, website blocking is not all rainbows and unicorns. Without any significant change to Sky’s blocking setup, more of these inadvertent blocks are bound to happen in the future.