LONDON/FRANKFURT: British broadband provider TalkTalk said it had received a ransom demand from an unidentified party claiming responsibility for a cyberattack that could have led to the theft of personal data from its more than 4 million customers.
The data could include credit card and bank details, and if the theft is confirmed by a police investigation it would be one of Britain's biggest online security breaches.
"We have been contacted by, I don't know whether it is an individual or a group, purporting to be the hacker," TalkTalk CEO Dido Harding told the BBC, without giving details.
Jens Monrad, a Copenhagen-based security expert for US cyber defence firm FireEye, also told Reuters that samples of financial data which appeared to come from TalkTalk customers had been spotted for sale in cybercriminal forums on the so-called dark web.
A TalkTalk spokeswoman declined to comment, citing the ongoing police investigation.
The attack is potentially one of the largest and most damaging to hit a British company, and follows dozens of high-profile cases targeting retailers and banks in North America.
The details of millions of customers of infidelity website Ashley Madison were leaked in August after a massive cyberassault, while Sony Corp's film studios were hit last year.
TalkTalk said late on Oct 22 there was a chance names, addresses, dates of birth, phone numbers, e-mail addresses, TalkTalk account information, credit card details and/or bank details had been accessed.
"Potentially this could affect all of our customers. I don't know for certain, which is why we are taking the precaution of reaching out to everyone," Harding told the BBC.
Third breach this year
The attack is the third data breach to hit TalkTalk this year, and experts said it would damage the reputation of the company, which competes with bigger rivals BT, Virgin Media and Sky in the broadband market.
"Their brand will be damaged and their customers will say it is the final straw," said computer security expert Graham Cluley.
Shares in TalkTalk, which had fallen 7% since the group's websites went down on Oct 21, fell as much as 8.5% on Oct 23 to a two-year low of £2.38 (RM15.51).
Some customers took to Twitter to vent their anger.
"I see #talktalk has been hacked again, seriously need to go to another provider, especially as I find out via BBC and not TalkTalk," said Cardiff-based user Lan.
Monrad said hackers seeking to exploit the value of stolen customer data often publish small samples of stolen data in order to attract buyers in the underworld who will in turn try and exploit customer details for financial gain.
"Our field intelligence operation has found what appears to be a direct dump of various database information from TalkTalk," he told Reuters in an interview.
He said the samples FireEye has collected contain specific bank account and credit card information from what appears to be TalkTalk customers.
A TalkTalk spokesman said the company was trying to determine whether key customer financial details and passwords were protected by encryption in the company's databases.
"We are still investigating the extent of information accessed and exactly what customer data may have been compromised," the spokesman said.
The Metropolitan Police said its cyber crime unit was investigating an alleged data theft from a telecommunications website, without giving details.
Personal data including names, addresses and phone numbers were stolen from TalkTalk at the start of the year, and in August servers owned by Carphone Warehouse, the retailer which founded TalkTalk, were attacked, potentially affecting 480,000 TalkTalk mobile customers. — Reuters