The UK’s NatWest and RBS’ online banking services suffered downtime for the second time in a week after a suspected attack by hackers.
The banking group reported that the crash, happening at 11.30am and lasting about an hour, was due to a DDoS attack, commonly used by hackers to bring down a website by sending millions of requests and overwhelming the server.
A spokesperson for NatWest said: "Due to a surge in internet traffic deliberately directed at the NatWest website, customers experienced difficulties accessing some of our customer websites today.
"This deliberate surge of traffic is commonly known as a distributed denial of service (DDoS) attack. We have taken the appropriate action to restore the affected web sites.
"At no time was there any risk to customers. We apologise for the inconvenience caused."
RBS and NatWest services also crashed on Cyber Monday (2 December), leaving many customers unable to pay for online purchases during the UK’s biggest online shopping event of the year.
The second crash, on 6 December led to angry customers taking to Twitter to vent their frustrations with the banking group.
Some claimed they could not use ATMs as well as being unable to access online banking.
The banking group has not yet suggested who might be responsible for the suspected attack on its systems.