Yahoo shares are sliding on worries that Verizon will walk away or slash its US$4.8 billion offer for the company's digital operations after another massive data breach. On Wednesday it was revealed that information was stolen from more than 1 billion user accounts after disclosing a separate hack of some 500 million accounts in September. The Internet company required all of its customers to reset their passwords a stronger measure than it took after the previous breach was discovered, when it only recommended a password reset. Yahoo also said Wednesday that it believes hackers responsible for the previous breach had also accessed the company’s proprietary code to learn how to forge “cookies” that would allow hackers to access an account without a password. The company was tentative in its description of new problems, saying the incident was “likely” distinct from the one it reported in September and that stolen information “may have included” names, e-mail addresses, telephone numbers, dates of birth, hashed passwords and, in some cases, encrypted or unencrypted security questions and answers. Verizon had said it would reevaluate the Yahoo deal after the first hack, and said the same Wednesday after the latest revelation. If the hacks drive Yahoo's users away, the company wouldn't be as valuable to Verizon in its quest to build a digital-ad business. Yahoo has sent an e-mail notice to potentially affected users that states, in part: "Please note that you'll receive a prompt in the desktop version of Yahoo Mail explaining that "Your account may have been affected by a security issue." This is a legitimate message from Yahoo and the link will bring you to the security issue FAQs page." It also states, "The email from Yahoo about this issue does not ask you to click on any links or contain attachments and does not request your personal information. If an email you receive about this issue prompts you to click on a link, download an attachment, or asks you for information, the email was not sent by Yahoo and may be an attempt to steal your personal information. Avoid clicking on links or downloading attachments from such suspicious emails." Source: ja observer, Yahoo, HuffPo