Zappos' failure to prevent a hacker from stealing the personal data of 24 million customers of the online shoe store has left the victims open to cyber-attacks on several fronts, experts say. Zappos, which is owned by Amazon (NSDQ:AMZN).com, reported the hack over the weekend, notifying customers via e-mail that a cyber-criminal had stolen names, e-mail addresses, billing and shipping addresses, phone numbers, scrambled passwords and the last four digits of credit card numbers. Chief Executive Tony Hsieh said in the message that a hacker had penetrated the company's internal network and computer systems through a server in Kentucky. No other details were released.