The details are a bit sparse right now, but Yahoo has just disclosed by way of their Tumblr that they’ve detected what they’re calling a “coordinated effort to gain unauthorized access to Yahoo Mail accounts”.
Yahoo didn’t disclose how many accounts were affected, but we’ve asked for clarification and will update the post accordingly. It’s possible that they’ve yet to nail down an exact number. Given that it was enough to disclose the news in a public blog post, it’s presumably a non-trivial amount.
The (sort of?) good news: it doesn’t appear that Yahoo’s own servers were compromised — instead, it looks like someone is firing off a bunch of login attempts using emails/passwords secured from an unnamed “third-party database compromise”. In other words: the attackers got someone else’s database of usernames/passwords, and are mass-checking for accounts that use them same credentials on Yahoo Mail.
In response to the attack, Yahoo has reset the passwords of all accounts that appear to have been affected. If you’re trying to log in and Yahoo is asking you to change your password and verify your identity via SMS, this is probably why.
[Photo credit: Scott Schiller on Flickr]