The banking arm of supermarket-chain Tesco has resumed normal service after shutting down for several days to protect itself from further losses in a widespread fraud that saw thousands of customers lose money from their online accounts.
The bank has revealed the theft cost it £2.5 million (A$4.01 million), taken from around 9000 customer accounts over the weekend. It has pledged to repay all the money to its account holders.
As many as 40,000 customers reported suspicious activity on their online banking accounts.
The theft triggered the suspension of online transactions on Monday by the bank for security purposes. It announced yesterday that it has now resumed full service.
The bank asserted that no customer data had been compromised in the incident.
Tesco Bank's CEO, Benny Higgins, said, “we've now refunded all customer accounts affected by fraud and lifted the suspension of online debit transactions so that customers can use their accounts as normal."
“Our first priority throughout this incident has been protecting and looking after our customers and we’d again like to apologise for the worry and inconvenience this issue has caused."
The UK's National Cyber Security Centre confirmed on Tuesday that it was working with Tesco and the National Crime Agency to investigate the attack, which has been described as "unprecedented" by the Financial Conduct Authority chief executive, Andrew Bailey.
The bank has still provided very little detail about what exactly happened over the weekend. It is not yet clear how criminals carried out the attack, and there has been no word yet if there are any suspects.
Meanwhile, some security experts have suggested that the cyber-attack on Tesco Bank could be an inside job. This is because cyber-criminals managed to steal money from a large number of accounts all in a short space of time.
Jonathan Sander, VP of product strategy at Lieberman Software said "the shape and scale of the attack on Tesco's customers does seem to suggest that there was an element of someone – or something – on the inside.”