22 million user IDs may be in the hands of hackers, after Yahoo Japan security breach

The call has gone out to Yahoo Japan’s 200 million users to change their passwords, after the company warned that it suspected hackers had managed to access a file containing 22 million user IDs.

Yahoo Japan says that it detected an attempt to gain unauthorised access to its administrative systems on Thursday at approximately 9pm local time.

Although the information taken from Yahoo Japan’s servers is said not to contain passwords, or other personal identifying information required to hijack an account (such as the answers to secret questions), the site has decided that users should reset their passwords regardless.

In a press statement published on Yahoo Japan’s website, the number one search engine in Japan stressed that it had not confirmed that the data had definitely leaked to the outside world, but that it deeply apologised for any inconvenience caused…

Read more in my article on Sophos’s Naked Security blog.

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Graham Cluley is a veteran of the cybersecurity industry, having worked for a number of security companies since the early 1990s when he wrote the first ever version of Dr Solomon's Anti-Virus Toolkit for Windows. Now an independent analyst, he regularly makes media appearances and is an international public speaker on the topic of cybersecurity, hackers, and online privacy. Follow him on Twitter, Mastodon, Bluesky, or drop him an email.