Millions of people could have had their credit card and bank details stolen after a "significant and sustained cyber-attack" on the TalkTalk website, the UK company says.
The phone and broadband provider, which has over four million UK customers, said banking details and personal information could have been accessed.
TalkTalk said last night that it was "too early to say" how many had been affected by the attack but urged users to change their passwords and check their bank accounts. They also said the site is now secure again.
We're joined by cyber security expert David McClelland who tells us more about the attack about how we can keep our personal information safe online.