Yahoo Japan says 22 million user IDs may have been stolen

Yahoo Japan, the country's largest Web portal, said up to 22 million user IDs may have been leaked during a hack that was discovered last week.

The company emphasized that the IDs are already public information, and no passwords or other private data were affected. Yahoo Japan IDs are used along with password to log in to the site, and are often displayed when users leave comments or use its shopping or auction services.

Yahoo Japan said it discovered illicit access to its ID servers on Thursday evening, and upon further investigation found a file with 22 million user IDs on it. The company said it wasn't sure if the file had been transferred outside of the company, but couldn't deny the possibility.