Analysis
BBC Business editor Kamal Ahmed
Small print matters. Some of TalkTalk's millions of customers might have been angry enough to try to terminate their contracts when the telecommunications company first revealed details of a major data security breach last month.
But, with contracts for mobile, fixed line, broadband and television services of up to two years (always worth looking at those few lines at the bottom of the paperwork) customers found they couldn't leave TalkTalk without incurring hefty costs.
When Dido Harding, the chief executive, first announced two weeks ago that customers would only be able to leave if they could show a "direct impact" on their bank account - a pretty high bar - investors heaved a sigh of relief and TalkTalk's share price bounced up.
It was up again this morning - by more than 12% - as the half-year results revealed that TalkTalk was still expected to make £300m profit before tax this year. And that revenues were up 6%.
Read Kamal's blog here.
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On 21 October, hackers attacked TalkTalk's website, stealing confidential customer data.
The firm was initially uncertain as to the extent of the hack, but after an investigation it said last week that 157,000 of its customers' personal details had been accessed.
More than 15,600 bank account numbers and sort codes were stolen. Four people have been arrested and bailed in connection with the hack.
Ms Harding told the BBC that it was "too early to tell" what the longer-term impact of the breach would be on the business.
"We of course saw an immediate spike in customers cancelling their direct debit, but actually after a few days we saw many of those customers reinstating their direct debits again, so time will tell, but the early signs are that customers think we are doing the right thing," she told BBC business editor Kamal Ahmed.
Paula Barrett, a partner at law firm Eversheds, said preventing cyber-attacks costs money, but not preventing them costs more.
"Today's announcement reinforces how significant the cost impact of this sort of event can be. There can be a very long cost tail to these scenarios, which may run for years as new systems and processes have to be adopted and claims handled," she said.