Cleanfeed (content blocking system)

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Cleanfeed is a content blocking system implemented in the UK by BT, Britain's largest Internet provider, which targets only illegal content (child pornography) identified by the Internet Watch Foundation. All UK ISPs will be obliged to implement a version of it by the end of 2007. Information on how this works is restricted to members of industry organisation LINX. [1] [2]

Cleanfeed was created in 2003 and went live in June 2004. [3]

The Internet Watch Foundation's aims include criminally obscene content and content that incites racial hatred. It is unknown whether images meeting those criteria are blocked by Cleanfeed.

1 Technical implementation
2 Filtering comparison
3 See also
4 External links

[edit] Technical implementation

There is a blacklist containing URLs to be blocked. Using Border Gateway Protocol (BGP) servers on the backbone routes traffic to IP addresses that match domains that appear in URLs in the blacklist to special HTTP proxy servers. These proxy servers then do the actual filtering by matching HTTP requests to URLs on the blacklist.

[edit] Filtering comparison

The other popular way of blocking content is DNS manipulation. Compared to this, Cleanfeed has the following properties:

Harder to circumvent. But still not that hard. Users can use proxy servers. Servers can use another port than 80.

Less collateral damage. DNS based blocking is criticized for blocking all content on a site with the same domain name. Cleanfeed only blocks what is explicitly blacklisted. E.g., it would be possible to block only one image in an article.