Analysis TalkTalk - it would seem - has blazed an unlikely trail for Britain's big name ISPs by being the first telco to switch on network level filtering of web content. Now, after many months resisting the urge to apply such controls to their services, the other major providers - BSkyB, Virgin Media and BT - have all decided to follow suit.

Your correspondent recently chaired an Internet Service Providers' Association event at which the panel and audience discussed how effective current measures were in protecting children online. The confab proved revealing - with BT and Virgin Media publicly stating for the first time that they too would be introducing network-level filters on their services later this year.

As we reported in February, BSkyB confirmed that it had concluded that computer-based parental controls were no longer enough to protect kids who use web-based services on a variety of devices. It will shortly begin filtering content using DNS lookup, the company's policy director Adam Kinsley disclosed during the debate.

And DNS lookup appears to be the preferred method: it's to be adopted by Virgin Media and BT, too.

Some might argue that the country's big name telcos have been strong-armed into agreeing to network-level filtering in a move to avoid regulatory action from the government. Interestingly, the industry's change of heart comes months after Prime Minister David Cameron labelled network-level filtering a "crude system".

He appeared to have softened his original stance at that stage, agreeing that ultimately it was up to parents to decide what their kids should and shouldn't view online. At that point, telcos - apart from TalkTalk with its enthusiasm for network-level blocking - continued to advocate the industry's Active Choice code by offering up software to allow their subscribers to manage the filtering of content on their own computers.

But the mood has now changed and the outcome - according to Sky's Kinsley - is good for public policy.

His company will soon introduce its "whole home" filtering system to customers on an opt-in basis. Kinsley admitted that the system itself was "not perfect" and wouldn't "solve all the problems" associated with protecting kids from supposedly harmful content, but he told me that "it feels like the right thing to do now".

Representatives from Virgin Media and BT both agreed about the timing of the shift in thinking but shared little at the event about their plans. Here's what VM is willing to tell us on the record:

We will be introducing a whole-home solution later this year and industry is working with government and other groups to keep kids safe online without the need for legislation.

And BT echoed that statement with this official response to The Register:

BT is introducing a network based parental controls solution that will cover all devices connected [to] a customer’s home broadband line.

We sought clarity from both telcos about where filtering on its network would be applied. Virgin Media remained vague about its plans. A spokesman told us:

'Whole home' means it works for every device brought into the home. A network level filter would equal a whole home solution, but it’s not the only way.

BT confirmed that it would happen at the ISP level, but no word yet on whether its system would be switched on by default for the telecom giant's subscribers.

Forcing people to opt out (that is, to opt IN for porn, what the internet is mainly used for - Ed) could be commercial suicide, so presumably - just like Sky's upcoming filter and TalkTalk's Homesafe product that is provided by Chinese vendor Huawei - customers with kids will be nagged to approve website blocking. That said, no ISP has yet explained how it will accurately determine the profile of its subscribers. How many customers, for example, when signing up for a broadband service state that they have children living in their house?

Late last month - as ISPs began making favourable sounds about network-level filtering - the government issued a progress report on the recommendations submitted by Reg Bailey on the commercialisation and sexualisation of childhood.

The Department for Education said it was "encouraged by evidence" from the UK's biggest ISPs that they would be "extending and strengthening their parental controls approach".

Whitehall's next move is to try and work out how to deal with age verification online. ISPs will be expected to come up with measures to ensure that the person setting up parental controls on their service is over the age of 18. Good luck with that! ®