Mobile operator Vodafone UK has made a cock-up of its attempt to correct a billing error, which saw customers being charged £5 when they signed-up for the providers free Mobile Internet Access promotion. Recognising the fault it promptly shot off an email to the 416 affected customers, only to do so by using the CC instead of BCC method - exposing all the private email addresses.

BCC (aka - Blind Carbon Copy) works by concealing individual email addresses from the complete list of recipients, thus allowing you to contact any number of people in a mass email without actually revealing who the other recipients are. By contrast CC is just a plain 'copy to' and allows everybody to see who the email is being sent to.

Vodafone has apologised and informs The Register that the problem occurred due to human error and it was the first time such an incident had ever occurred with them. Situations like this are generally quite uncommon but they do happen.