A web expert has found that O2 is sharing the mobile phone numbers of its customers with third parties through its website.
According to Lewis Peckover, the telephone numbers are included in plain text format so that website owners can use them for marketing purposes.
While the leaking of mobile numbers to third parties does not appear to be universal, many O2 customers will be affected.
Commenting on the discovery, security expert at Sophos Graham Cluley claimed the problem is not a new one and has been affecting O2 for at least two years.
Writing on his security blog, Mr Cluley claimed: "My guess is that it's more likely to be a cock-up than malice which caused this data to be leaked – but what's worse is that the problem is still present almost two years after it was first discovered."
The lax security when it comes to customers' mobile phone numbers could cost the company contracts, but O2 said it is investigating the claims.
Posted by Samantha Green