Yahoo Japan reports suspected leak of millions of user IDs

Yahoo Japan Corp reported on Friday night, a suspected leak of up to 22 million of its user IDs and detection of an unauthorised attempt to access the administrative system of its web portal Yahoo Japan, according to the Kyodo news agency.

The agency added, the leaked information did not include passwords and data necessary for identity verification to reset passwords, the agency said.

Kyodo reported that the company detected the access attempt at around 9 pm on Thursday.

Yahoo Japan checked its system following severing of access and came across signs that an attempt had been made to steal user IDs, according to Kyodo.

Yahoo Inc holds a 35 per cent stake in Yahoo Japan, while Japan's mobile phone operator SoftBank holds a 35.5-per cent stake.

"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 late Friday.

Yahoo Japan said it had updated its security measures to prevent a repeat of the incident.

Its popular portal Yahoo! Japan holds the top search engine position in Japan with a 50 per cent plus market share, as against 40 per cent for rival Google.

In 2011, Sony said, after hacker attacks on PlayStation Network and Sony Online Entertainment, information including usernames, passwords and birth dates of over 100 million people may have been compromised.

Japan acknowledged that its preventative measures against cyberattacks remained underdeveloped, with the national police agency having announced this month it would launch a team to analyse and combat cyberattacks.

The Japan Aerospace Exploration Agency said last month that an unauthorised attempt to access its system might have compromised information related to the International Space Station in an unauthorised attempt to access its system.