“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 is 35.5 percent held by Japan’s mobile phone operator SoftBank, and 34.7 percent held by US Internet giant Yahoo! Inc.
The attack on Yahoo Japan’s administration system was spotted late on 16 May, said the company in a statement. When the attack was detected, the tech firm cut net access while it investigated.