Yahoo Japan has recommended its 200 million customers to change their passwords after it was discovered that the personal data of 22 million users of the service may have been stolen.
The intrusion into Yahoo Japan systems occurred on May 16. After that the access to the service was closed.
“We don’t know if the file (of 22 million user IDs) was leaked or not, but we can’t deny the possibility, given the volume of traffic between our server and external terminals”, the company said in an official statement.
The company recommended its users to change their passwords although the stolen information did not include passwords and the kind of data necessary to verify a user’s identity. Still Yahoo Japan updated its security measures to prevent a repeat of the incident.
The hackers have already tried to break into Yahoo Japan last month. Their motives are still unknown.
