TalkTalk has received a ransom demand from someone claiming to be behind a cyber attack which may have resulted in sensitive data belonging to millions of its customers being stolen, the company said.
The telecoms giant is investigating whether credit card and bank details were taken in Wednesday's attack, the third time this year it has been the victim of a cyber crime.
A TalkTalk spokeswoman said: "We can confirm we were contacted by someone claiming to be responsible and seeking payment."