TalkTalk cyber attack will cost company up to £35m

“Our customers will judge us on our actions, not our words”, she said.

The company says the total number of customers whose personal details were accessed is 156,959, and of this number 15,656 bank account numbers and sort codes were accessed.

Net earnings after interest, taxes, depreciation and amortisation slipped 18 per cent to £90m, against £110m for the same period previous year.

The announcement was made the same day that TalkTalk reported revenue in the first six months of fiscal 2016 grew to £912 million from £871 million a year earlier.

Dido Harding, TalkTalk’s chief executive, said the company had contacted all customers directly affected and is writing to all customers outlining how it intends to protect itself from future attacks.

On 21 October, hackers assaulted the web site of TalkTalk, stealing private customer information.

TalkTalk said it will offer free upgrades to all customers, but those who want to terminate their contract following the cyber-breach will not be able to do so for free.

An upgrade will be available to all customers – even those unaffected by the hack – from December 1. The costs are part of TalkTalk’s bid to instil confidence in the business, which has been hacked three times in the last 12 months.

On its dedicated upgrade page, the company lists four options: there’s free TV content, which includes movies, kids entertainment and sport; a mobile SIM, with a monthly allowance of free texts, data and calls; Unlimited United Kingdom landline and mobile calls and a broadband health check from TalkTalk engineers.

Only 157,000 customers were affected, it later said, but Harding had no regrets about going public so soon.

The group has also created a new bundle of online and telephone security features to boost customer protection.

Ms Harding insisted the firm had a “robust plan to deliver a significant step-up in profits in the second half, underpinned by the benefits of our transformation programme coming through strongly”.

“We have delivered half year results in line with our plan and revenue growth accelerated strongly through the second quarter”. In the recent attack, it was discovered that not all customers’ data was encrypted.