Yahoo says usernames and passwords of its email customers have been stolen and used to access accounts, but the company isn�t saying how many accounts have been affected.

The company said in a blog post that �The information sought in the attack seems to be names and email addresses from the affected accounts� most recent sent emails.�

Yahoo says it believes the usernames and passwords weren�t collected from its own systems, but from a third-party database. The company says it is resetting passwords on affected accounts and has �implemented additional measures� to block further attacks.

The company would not comment beyond the information in its blog post. It says it is working with federal law enforcement.

(AP)