Internet giant--no, we're not talking about Google--Yahoo has seen a breach of its security. An undisclosed number of e-mail addresses and passwords, collectively accounts, were compromised, Yahoo informed users via its Tumblr page. Yahoo says, "Upon discovery, we took immediate action to protect our users, prompting them to reset passwords on impacted accounts."
Yahoo believes that the information was obtained from a third-party database, not their own systems, but they are working with law enforcement to hopefully find the perpetrators and bring them to justice. Yahoo says that they have implemented additional measures to keep accounts safe. Impacted accounts have had their passwords changed and Yahoo is allowing "second sign-in verification" to allow users to regain access.
If your account was compromised, you may have received an e-mail notification or SMS, if you had added a mobile phone to your account. As always, Yahoo reiterates good user security:
In addition to adopting better password practices by changing your password regularly and using different variations of symbols and characters, users should never use the same password on multiple sites or services. Using the same password on multiple sites or services makes users particularly vulnerable to these types of attacks.