US banking giant Citigroup has told its clients that about 360,000 credit cards were affected by a hacking attack last month — nearly twice the number previously acknowledged.
The security breach had compromised a total of 360,083 North America Citi-branded credit cards, Citigroup said late Wednesday. The company had earlier said that the attack impacted around 210,000 credit card customer accounts — roughly 1% of its US clientele.
“Citi has implemented enhanced procedures to prevent a recurrence of this type of event. We have also notified law enforcement and government officials,” it said in a statement to “our customers.”
“We continue to monitor customer service and communication channels and take every necessary action to ensure our customers are cared for.”
It declined to provide further details of the breach, citing the ongoing investigation and its customers’ security. The company has come under scrutiny from US lawmakers for its handling of the attack. Citi did not inform its clients of the May 10 attack until nearly a month later.