Technology giant Yahoo disclosed Wednesday that hackers had broken into more than one billion of its user accounts, starting three years ago, and stolen personal information including addresses, telephone numbers, dates of birth and security questions. Yahoo had said in September that 500,000 other accounts were compromised but denied that they included credit card or other financial information. The "Krebs on Security" website said that the hackers were able to copy the "cookies" that Yahoo, like many other internet sites, implants in the computers of users who log in. Those text files contain valuable information including authentication that enables the user to avoid re-entering his or her name and password. Anyone who has Yahoo cookies can enter any of the company's user accounts without identification.