Travelex, the currency exchange group, is in the midst of a cyber attack which has left some customers with no travel money.
The criminals behind the hack told the BBC they are demanding $6m (£4.6m) or company computer systems will be deleted and customer data sold online.
Dr Sandra Scott-Hayward, cyber security expert at Queens University Belfast, says that the attack appears to be “quite sophisticated”.
She tells Wake Up To Money that it appears that the attackers have been able to access Travelex’s network because of a “software vulnerability in one of their servers”.
“This particular attack looks quite sophisticated in the way that it hides itself,” says Dr Scott-Hayward.
“The attack will always try to hide where it is on the network and we generally don’t find out until much later after an actual attack that data may have been stolen – it takes so long to be discovered on the system.”