Some Tesco Bank customers have had their credit cards cancelled following concerns about accounts potentially being compromised.
Those affected have received texts and they will receive new cards around a week later.
Tesco Bank said only a tiny proportion of its three million credit card customers have been affected.
The bank said the step has been taken as a "precautionary measure" and it is the result of routine industry-wide efforts to protect people against fraud.
The precautionary action has been taken as a result of a suspected third party compromise.
A Tesco Bank spokesman said: "We take the security of our customers' accounts very seriously and take every measure possible to protect customers from fraudulent activity.
"As a result of routine industry-wide fraud protection measures, we have reissued a number of credit cards as a precautionary measure.
"We apologise to our customers for any inconvenience caused as a result."
In 2016, a cyber attack forced the lender to pay out £2.5 million to 9,000 customers who had money stolen from their accounts.