Under-pressure telecom group TalkTalk (LON:TALK) had another £200mln wiped off its market value in the wake of the cyber-attack it suffered last Wednesday.
Shares dropped a further 8.5% to 235p, taking the total wiped off its market cap to £500mln in the last four business days.
It could get more expensive yet for the firm, with reports suggesting it could have to shell out £1,000 per affected customer.
The company is also offering a year’s free credit checking service to its 4.2mln customers, which will come at a cost.
Berenberg said: “A worst-case would be to take a typical credit checking offer (eg Experian at £14.99 pcm), take a haircut for big customer like TalkTalk, say 50%, and apply that cost for 4.2mln customers over 12 months – the impact would be £280mln, which would wipe out this year’s EBITDA, and more.”
Personal details as well as credit card and/or bank details may have been compromised, but Dido Harding, chief executive, said it would be impossible for customers to lose money from the attack.
“No banking details were taken that you wouldn’t already be sharing when you write a cheque, or give to someone so they can pay money into your account,” she said.
Harding added the number of customers affected and the amount of data stolen was smaller than had been originally feared, as only the website was attacked, not TalkTalk’s core systems.
It is the third data breach this year for TalkTalk, which has yet to confirm the number of customers affected.
On Friday, TalkTalk received a demand for money from a company purporting to have perpetrated the security breach.