BT launched a trial of the technology on 21st June, with the intention of blocking access for BT internet customers to any web site named on a blacklist compiled by the Internet Watch Foundation (IWF).
The UK-based watchdog's blacklist relates to worldwide child sexual abuse web sites that have been assessed as "illegal to view" in the UK. It is collated from reports the IWF receives via its internet hotline and grows by more than 3,000 potentially illegal child abuse web sites every year.
The system used by BT, known internally as Cleanfeed, works by blocking requests from subscribers to access the blacklisted sites, returning an error page instead. BT logs the access request, but no user details are retained, according to the telco. "BT has no means of identifying the individuals whose attempts have been blocked," according to its statement.
BT revealed yesterday that between 21st June and 13th July it had blocked 230,000 attempts to access illegal sites. BT points out that this figure includes repeated attempts by individuals and so does not represent a total of the number of people trying to gain access to these sites.
According to the BBC, the IWF declared the results "staggering", and a police spokesman described the implications as "extremely disturbing".
Speaking on the BBC's Today programme, Home Office minister Paul Goggins said: "Every image of a child that appears on the internet is an image of a child that's abused." He called the figures "deeply shocking" and urged other ISPs to take advantage of BT's offer to allow them use of the technology.
But ISPs are not convinced. Speaking to ZDNet News, AOL UK's director of communications, Jonathan Lambeth, said that it was easy for BT to use this type of technology because it only has to deal with its own network. But other ISPs use a variety of networks, and would not be able to use Cleanfeed until all of these networks had adopted the technology.
In addition, said Lambeth, there was the ever-present prospect of being sued if a legal site was included in the blacklist.
The scheme is also provoking controversy among privacy advocates, who see Cleanfeed as the first step down the slippery slope to internet censorship – until now the province of oppressive regimes such as those in China and Zimbabwe.
Other critics point out that it is easy for porn sites to change their web address, and thus avoid the blacklist. In addition, porn accessible through peer-to-peer networks or spam e-mail remains unchecked.
BT readily admits this:
"BT does not pretend that this trial will offer a total solution to this problem, or that BT alone could provide such a solution, but we believe it is an important step in the right direction," the company said in a statement.