Yahoo has admitted yet another cyber attack but this time one billion user accounts may have been affected.<br />The hack dates back to 2013 and the scale makes it the largest breach in history.<br /><br /> The internet giant says names, phone numbers, passwords and email addresses were stolen, but not bank and payment data. <br /><br /> Last September Yahoo disclosed a 2014 breach affecting 500 million users which it blamed on hackers working on behalf of a government.<br /><br /> IT HAPPENED AGAIN: Yahoo says a billion user accounts were stolen in possibly the biggest hack of all time https://t.co/qLZ5EUWyTO— deray mckesson (@deray) December 14, 2016<br /><br /> The news is a further blow to CEO Marissa Mayer who joined Yahoo in 2012 charged with bringing the company into the smartphone era. However experts say this second breach points to a pattern of serious failures.<br /><br /> Mayer is currently negotiating the sale of Yahoo’s core business to Verizon Communications.<br /><br /> Following the 2014 attack Verizon allegedly devalued Yahoo by one billion dollars. This latest disclosure raises fresh questions about its $4.8bn offer and whether the US mobile carrier will abandon its bid altogether.<br />
