Tokyo, May 19: Yahoo Japan Corp. has said it suspects up to 22 million user IDs may have been stolen during an unauthorised attempt to access the administrative system of its Yahoo! Japan portal.
"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 a statement.
The information did not include passwords and data necessary to verify a user's identity or reset passwords, it said, adding that the company had updated its security measures to prevent a repeat of the incident.
Yahoo Japan is 35.5 per cent held by Japan's mobile phone operator SoftBank, and 34.7 per cent held by Yahoo! Inc. Its popular portal Yahoo! Japan holds the top search engine position in Japan with a more than 50 per cent market share, compared with around 40 per cent for rival Google.
In 2011, Sony said information such as usernames, passwords and birth dates of more than 100 million people may have been compromised after hackers struck the PlayStation Network and Sony Online Entertainment services.
Japan's national police agency announced this month it would launch a team to analyse and combat cyberattacks.
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