Is O2 sending your Mobile number to every website you visit.

January 25, 2012

Seems that O2 maybe sending you mobile number to websites you visit. @lewispeckover has created a script to interrogate.

As he states:

“If you’re on O2’s UK mobile network (not ADSL), you’ll (probably) see a line beginning with x-up-calling-line-id – followed by your mobile phone number in plain text.”

O2 appears to send your number in the host header. The host header is information sent from the browser to web server to enable the server to make decisions on your devices, or browsers, capabilities.

He goes on to say,

“O2 seem to be transparently proxying HTTP traffic and inserting this header.”

This may or may not be a problem for you but there appear to be no way to opt of of this invasion of privacy.

Check the Script

To test, navigate to this page and look out for x-up-calling-line-id.

How to bypass

To get around this issue you can change your Access Point Name (APN).

Use the APN “” with a username of “bypass” and a password of “password”.