December 19, 2011 | Kayahan Cantekin

How does mobile Internet filtering work?

All the major UK mobile operators have Internet filtering schemes that block certain content from users. These filters are designed to protect children from accessing adult material. The filters are turned on by default when anybody signs up to a mobile contract. Age verification, normally via a credit card, is required to turn them off. We've heard a lot of anecdotal evidence of mistakes, over-blocking and the difficulty of pointing out when things go wrong (for example, see James Firth's blog on Vodafone's blocking of underwear sites).

Mobile Internet access is becoming more important as a means of getting online. According to Ofcom, 28% of UK adults said they accessed the internet on their mobile in the first three months of 2011, and mobile data use increased forty-fold between 2007 and 2010. We've started to look more closely at how this blocking works.

It's clear that mobile operators could be much clearer about this. They tend to be pretty opaque as to exactly how their filtering works, and how they decide which Web pages are inappropriate for under 18s.

For example, Orange says that it is the Independent Mobile Classification Body (IMCB) that decides what is adult content or not (see here). However this is not true. The IMCB does provide a framework for determining content that is inappropriate for children and teenagers. But content from the Internet is out of IMCB’s remit, as stated in its Classification Framework (see here). We've been in touch with IMCB about this, and are awaiting a reply.

Mobile operators all declare that they are acting according to a ‘code of conduct’ set by the Mobile Broadband Group. But this code does not provide for any kind of criteria for determining or defining blockable content. It simply points at the IMCB framework.

It is most likely that security contractors and their algorithms employed by mobile operators, such as US companies like Blue Coat, decide what we are able to access. How the policies of these companies fit with the frameworks of the IMCB and the Mobile Broadband Group is another question we are looking to answer. 

As well as a lack of transparency, overblocking and clumsy customer support, there is also plenty of controversy surrounding the methods these security companies use, for example about how much user data they keep hold of and the consent issues raised by the retention of this data. There are also questions about some of these companies seemingly selling their filtering technology to oppressive regimes such as Syria and Burma.

Transparency regarding how mobile operators decide what counts as 'blockable' content is increasingly important. Customers should be able to ascertain how and why content is blocked, and have easier ways to point out when things are going wrong. We'll be developing more work on this, including tools to help you point out when mobile operators are blocking sites, soon. Please let us know if you're interested in helping out.

Comments (8)

  1. Suw:
    Dec 19, 2011 at 02:46 PM

    What I really don't understand is why the mobile companies don't just simply verify your age when you start the contract or buy a sim and adjust the settings accordingly. Given that they do credit checks and other such things, it should be trivially easy to add in a step where they check who the phone is for and whether the person paying wishes nanny filtering to be turned on or not.

    Forcing everyone to jump through these rather stupid hoops - and let's face it, any enterprising teen can get hold of a parent's credit card and fake the check - is pointless and one wonders whether the real aim is not to check your age, but to make use of the money that they take from your credit card and then later refund as a way of earning some interest. All those £1s must add up.

    But we also have to ask whether filtering actually does what it is supposed to, and that is to protect youngsters from inappropriate content. I have a suspicion that parental involvement is a bigger predictor of whether a child/teen is going to access inappropriate content than whether the phone has a filter on or not.

  2. Mark Pack:
    Dec 19, 2011 at 04:07 PM

    When I was a Vodafone mobile broadband customer last year, I had the strange experience of finding the default adult filter block meant I could not access any photos on Flickr. To call that a crude blunderbuss of a filter would perhaps be too kind :)

  3. Titania Bonham-Smythe:
    Dec 19, 2011 at 04:31 PM

    Second sentence: "...sings up to..."

  4. Peter Bradwell:
    Dec 19, 2011 at 04:38 PM

    Thanks Titania! Amended. Although maybe 'singing up' to a mobile contract is an idea with legs? Would certainly be more fun!

  5. Richard Maguire:
    Dec 19, 2011 at 04:42 PM

    I've experienced similar difficulties. I recently got a new contract phone from O2. Filtering of web content was on by default, despite the fact that this phone was purchased by myself, for myself and using several proofs of identity. Most of these pieces of paperwork included my date of birth, and as someone above pointed out, the agencies they use for credit checking also hold by date of birth - a quick check at the time is surely not too much to ask? Maybe a checkbox on the advisors computer in the shop, or one on the details page if buying online. After attemping to access the message board of a poker website and getting bounced back to an O2 landing page, i gave customer service a call. Another tip for O2? If you are going to force EVERY customer to ring up and confirm their age, how about the customer service rep doesn't treat you like a pervert because you want the filter removed.

  6. Simon:
    Dec 19, 2011 at 08:01 PM

    Don't get hung up on the age check commenters, the bigger issue is process.

    Besides the UK age constraints are ridiculous anyway, you have to be 18 to watch people do stuff on the Internet you can legally do (and watch in person as long as it is for free) at 16?!

    Where ever I've seen filtering controlled by private companies there has nearly always been accusations of commercial bias. Often accompanied by clear evidence that commercial bias was affecting filtering results.

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  8. Patrick:
    Dec 21, 2011 at 09:51 AM

    3 block access to adult material, supposedly in order to protect children using the handsets. Guess what the page that shows the block contains links to? You guessed it: porn.

    You really can't make this sort of stuff up.

    I had no problems growing up without a mobile phone. This was no doubt also the case for countless generations before me. Why then is there this assumption that children should be allowed to buy or use mobile phones? Here's a simple solution that will get rid of unwanted invasions of privacy: only allow adults to buy the handsets/contracts and get them to decide during the sale if filtering is required.

    And never mind overblocking: 3 and other mobile operators are breaking the law by intercepting and sharing traffic half way around the world without any sort of notification or consent from the customer (or for that matter from the owners of the websites being visited). Any webmaster interested in such things will also know how to tailor a page for the bots, and another for the real visitor that contains all the nasty stuff.

    From what I've been told several malware-laden sites already use this sort of tactic to try and evade the efforts made to limit the spread of malware. The search engine bots only ever sees a clean page but visitors going to the site through those same search engines get infected by the malware.

    Would anybody here care to bet that the same sort of thing can't be done with websites that would normally be deemed to contain adult material when it comes to Bluecoat bots or bots belonging to the ISP itself?