Yahoo has diclosed via Tumblr that they have detecte a coordinated mass hack attempt on Yahoo Mail accounts, according to TechCrunch.

The details of the matter are still very few right now, but Yahoo calls it a "coordinated effort to gain unauthorized access to Yahoo Mail accounts." The company did not disclose the number of accounts affected. Yahoo is possibly still trying to determine the exact number. since the hacking attempt was disclosed in a public blog, it might be a big number, the report explained.

The servers of Yahoo do not appear to be compromised. It would seem that someone has secured email or passwords and are firing off various login attempts using those details. In other words, the hackers are mass-checking if the same login details are being used on Yahoo Mail, the report detailed. 

As a response to the hacking attempt, Yahoo has reset all the account passwords that appear to have been affected by the attack. Affected users will encounter a request for password change or identity verification via SMS during the log in process, TechCrunch reported.