The Dutch central bank has warned that a quarter of all cyber attacks worldwide are targeting financial institutions and this means “in extreme cases” people would be unable to access their money.

Cyber attacks are carried out not only by criminal hacker groups, but also by other countries, the bank said, in its latest report on the financial stability of the Dutch economy.

“The cyber landscape is becoming increasingly complex, due in part to the rise of artificial intelligence,” the bank said. “AI offers opportunities, for example in the fight against cyber attacks, but at the same time hackers are also using AI to carry out more frequent and sophisticated attacks.”

In addition, the financial sector is vulnerable to incidents affecting third parties such as cloud storage which has been outsourced to a small group of service providers, the report said. Dependence on telecom services for vital processes also plays a role.

“It is important that financial institutions thoroughly understand these vulnerabilities, share information to mitigate cyber risks and prepare crisis measures,” the bank said. “Society should also be aware that a cyber attack could, in extreme cases, make financial services temporarily unavailable.”

The bank’s monetary affairs chief Olaf Sleijpen told the Financieele Dagblad people should not assume that payments system will always work.

“You might not be able to make pin payments for some time,” he told the paper. “Then you need to have cash under the mattress, or be able to pay with QR codes.”