  If you reside in the UK and you are one of the millions of
subscribers to mobile operator O2, you may be alarmed to learn
that the carrier is sending your mobile number to every website
you visit on your mobile phone.    What is x-up-calling-line-id?
Your mobile phone number.  We tested it on an O2-connected
mobile device and received the following results (number blurred
for privacy):  o2 520x780 UK mobile operator O2 sends your phone
number to every website you visit  O2 appears to be aware of the
issue and is replying to irate customers via its Twitter
account:  In our tests we have confirmed that Orange, T-Mobile,
Three and Vodafone do not send mobile numbers in header
information. If you are on GiffGaff (an O2-owned company) or
Tesco Mobile (which uses O2′s networks), you will be sending
your mobile number to websites also.  You also need to be
connected to its network, not a Wi-Fi connection.  Last night,
O2 replied to Lewis Peckover on Twitter, detailing why it sent
the data to websites:  However, Th