Update: O2 claims to have fixed the issue -- and indeed, two O2 phones we've tested are no longer displaying their numbers on the test site. Read more about O2's response here. Original story follows:
As O2 customers are getting riled up over news that the bubbly-blue network has been sharing your mobile number with websites you visit from your phone, a security expert reckons networks leaking your information is nothing new.
Security bod Graham Cluley says the issue goes back several years. On his blog, Cluley cites a paper presented by Berlin student Collin Mulliner entitled "Privacy Leaks in Mobile Phone Internet Access".
The aptly titled paper describes an investigation into how network operators are leaking personal information -- including your phone number -- to sites you visit while connected to their network.
Mulliner set up a test page you can visit to see what -- if any -- information your phone is betraying. If the page goes green, you're okay. If it shows up red, that means something's awry. We tried the page using one of the O2 SIMs we tested earlier today, and our phone number popped up yet again. Oh dear.
Mulliner's discovery was presented at a security conference back in 2010. In the slides for his presentation, he says he will never log any information from visitors to his test page, but obviously we can't vouch for that.
Meanwhile, in the present day, O2 is tweeting at disgruntled customers, telling them it's "investigating" the issue and that it's a "top priority". GiffGaff and Tesco Mobile are also susceptible to the problem, at least on the SIMs we tried. That's not surprising, because they both piggyback on O2's network. We haven't found any other UK networks leaking mobile numbers, however.
Obviously having your number leaked to all and sundry is no good, and one video that's appeared online shows how once a site has your number, it could use it to send spam text messages.
Are you an O2 customer? How does this make you feel? Will you be cancelling your contract, or is this a fuss over nothing? Tell us in the comments or on our Facebook wall.