Almost 2,000 Vodafone customers have had their bank details and personal information stolen.
But in a bizarre twist, the firm says criminals accessed their information from an “external source” and that their internal systems were not compromised.
The company has confirmed 1827 customers have had personal information stolen today.
Vodafone said the attacker got access to customers’ names, mobile numbers, bank sort codes and the last four digits of their bank accounts.
The trove of information was stolen from outside the organisation but they did not say how an external source had access to customers’ personal details.
The operator which has 19.5 million customers in Britain have not provided any further information or guidance for those who may be affected by “phishing” messages that try to extract more personal data.
A Vodafone spokesman said: “This incident was driven by criminals using email addresses and passwords acquired from an unknown source external to Vodafone.
“Vodafone’s systems were not compromised or breached in any way.”
Vodafone said it is also contacting affected customers and helping them to change their account details.
They added: “Our investigation and mitigating actions have meant that only a handful of customers have been subject to any attempts to use this data for fraudulent activity on their Vodafone accounts.