Yahoo announced today on its Tumblr blog that it detected a mass attack on its Yahoo mail server. The company describes the attack as a “coordinated effort to gain unauthorized access to Yahoo Mail accounts.” As a precaution, the company has rest the passwords of affected accounts. Yahoo said its servers were not compromised and believes the attackers are using username and password data obtained from a third-party source.
“Security attacks are unfortunately becoming a more regular occurrence. Recently, we identified a coordinated effort to gain unauthorized access to Yahoo Mail accounts. Upon discovery, we took immediate action to protect our users, prompting them to reset passwords on impacted accounts.
Based on our current findings, the list of usernames and passwords that were used to execute the attack was likely collected from a third-party database compromise. We have no evidence that they were obtained directly from Yahoo’s systems. Our ongoing investigation shows that malicious computer software used the list of usernames and passwords to access Yahoo Mail accounts. The information sought in the attack seems to be names and email addresses from the affected accounts’ most recent sent emails.”
Yahoo has reset passwords on accounts targeted in the attack, The company also is enabling second sign-in verification to allow users to secure their accounts from future attack. Yahoo advises all its Mail users to change their passwords on a regular basis and cautions them to never use the same password on multiple sites or services.