TalkTalk has been left red faced after its adult content filter failed to block access to one of the web's biggest explicit video sites.
The HomeSafe product has been widely endorsed by politicians because its network-based nature means it theoretically protects all devices within the home.
However, a bug in the system left some of its 4.1 million customers exposed to pornographic video content.
According to a report in The Daily Telegraph, the flaw was discovered by a mother of three who was testing the filtering system.
“The ‘You have been blocked’ page has been diverted to an advertising slot within the Pornhub homepage, thus opening access to it,” IT consultant Cherith Hately told the paper, which rated the site as the third biggest porn purveyor online.
“The HomeSafe barrier has been knocked down, technically and literally. TalkTalk should inform all their HomeSafe customers that their children are still able to see pornography so that parents can supervise more,” she said.
TalkTalk has acknowledged the failure and said it was working on a fix, but the ISP said the glitch did not affect all customers.
“We are aware that a customer using HomeSafe has been able to access a site which they had selected to block," the company said in a statement.
"We’re satisfied this site is not available to the majority of customers who have chosen to restrict this subject matter and we’re testing a technical solution which will fully resolve this issue.
"While no technical solution alone is able to solve the issue of child internet safety or be a substitute for parental supervision, we firmly believe that HomeSafe is a step in the right direction with over a million web pages blocked at customers’ request since May.”
Porn blocking has taken a front seat recently, with politicians pushing ISPs to improve parental controls for end users and a code of conduct outlining that ISPs should make new customers aware of control options at the point of sale.
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