Analysis BT has begun fleshing out its plans to block its Internet users from accessing websites containing illegal images of child abuse.
The system, called Cleanfeed, will censor access to several thousand websites on a blacklist compiled by UK Internet trade body, the Internet Watch Foundation (IWF). The blacklist features sites contain images of child sexual abuse that are "illegal to view" in the UK, under the 1978 Child Protection Act.
Conventional wisdom has it that applying censorship to control access to paedophile material online is beyond the scope of existing technologies and plagued by practical difficulties. However BT reckons it has come up with a workable - if still only partial - response to the problem.
Mike Galvin, director of Internet operations BT Retail, explained that Cleanfeed will only filter website traffic and will have no effect on material transmitted through P2P networks or via email. "Cleanfeed only looks at port 80 traffic. It's not a complete solution," he told El Reg.
How it works
Cleanfeed uses a two-stage filtering process. Firstly an access control list on a bank of Cisco routers re-directs BT customers who make a request to access suspect websites to an array of caches. Other traffic passes through virtually unimpeded. The array of Network Appliance caches is programmed to serve an error page, stored in the cache, whenever a request to access am IWF blacklisted website is made.
Galvin said: "If the URL of not on list, Cleanfeed won't stop it. This is designed to block casual access to child abuse material on the Net. It won't stop a hardened paedophile and we're not saying that. One of the things we want to cut down on is unintentional access to this kind of material. We're aimed this technology at Web access because this is the most universal means of accessing this kind of content."
BT is testing the system and plans to introduce it with its own BT Retail customers in a matter of weeks, a debut which has been accelerated by a weekend report in The Observer about the scheme.
The monster telco is also prepared to make its technology available to other ISPs on a wholesale basis. It claims to be already is discussion with others service providers. The Cleanfeed trial has the backing and support of the Home Office but BT said it thought of the idea itself and pushed forward the idea as a means of becoming a more responsible corporate citizen.
"This is a voluntary act by BT. I've no idea if anyone will follow," said Galvin. "If this kind of technology was made mandatory there would have to be changes in the law."
The US state of Pennsylvania has been forcing ISPs to block access to child abuse websites for some time but this is very much the exception rather than the rule.
Concerns about the system have focused on the accuracy on the blacklist. Already doubts have been expressed that no sooner has a site been blacklisted before it changes its host or URL and re-appears somewhere else. BT does not have a role in compiling the blacklist, and Galvin referred our questions on this over to the IWF.
Peter Robbins, chief exec of the Internet Watch Foundation, said the blacklist it compiled was dynamic and updated every week with around 60 new sites. Between 3,000 - 3,500 sites hosting illegal child abuse content are on its list. Paedophiles have been known to hack into websites to host illegal content, an incident that might potentially leave a company or university server blocked for months after illegal content is purged. Robbins acknowledged that hijacking happens but says this is rare. Organisations who find themselves unfairly blocked can go through an established appeals procedure, he added.
BT's initiative is been closely watched by the Internet industry as a whole. The Internet Services Providers' Association (ISPA) said it is nothing new for it and its members have a zero tolerance of illegal child abuse content. ISPA is clean to play down any perception that ISPs need only follow BT's lead in order to curtail the availability of child abuse images on the Net.
ISPA said: "Each ISP has a different infrastructure. This means that there is no 'one size fits' all technical solution to preventing access to websites offering illegal images in territories outside of the UK. As with any technical solution, care must be taken to ensure blocking websites offering illegal images does not cause collateral damage. Any such technical measures installed by ISPs must be evaluated over time to judge their success.
"The Cleanfeed solution now under trial by BT will only prevent 'casual' browsing of known websites. It will not hinder organised distribution of such images. It will not prevent access to new websites offering illegal content, nor will it prevent children being abused," it added. ®