Hackers may have stolen details of between 110,000 and 750,000 members of Japan Airlines’ frequent flier club, the airline said, blaming a virus attack on computer terminals within its network.
The data includes the names, addresses, genders and places of work of members of JAL’s mileage program, the airline said Wednesday.
JAL said it has not identified a leak of credit card numbers or passwords, and that no financial damage has been reported.
The airline detected a number of intrusions on Friday and Monday into the system that manages customer information.
An investigation found that 23 personal computers contained a virus. Seven were found to have been sending data to a server in Hong Kong.
The airline said the data breach may have begun Aug. 18, which would mean it had been going on undetected for more than a month.
JAL believes the breach began with a rogue email that introduced a virus to its network.
It reported to the case to Tokyo police.
In February, attackers penetrated a JAL service that allowed frequent fliers to exchange mileage points for gift coupons accepted by Amazon.com Inc. They racked up millions of yen in losses.
JAL said it will postpone the service’s planned restart, even though the two attacks appear to be unrelated.