Hackers in China attempted to access over 20 million accounts on Alibaba's e-commerce site Taobao last year.
A police investigation shows hackers obtained 99 million user names and passwords from a number of websites, over 20 million of which were also being used for Taobao accounts.
The hackers were discovered by Alibaba in November after they tried inputting details into Taobao.
Earlier, it was reported that hackers had used Alibaba's own cloud computing to access users' accounts in Taobao. But a spokesperson for Alibaba has denied that report, saying the hackers had used outside software to attack the site instead of Alibaba's cloud service.
Meanwhile, the spokesperson said the company detected the hacking in "the first instance," and reminded users to regularly change passwords.
