This is the first case in Beijing involving the theft of data from overseas users, state-run Global Times quoted an police official as saying.
China in the past denied allegation from US and EU that Chinese hackers carried out attacks on foreign tech companies to steal data.
The malware, called "fireball", developed by a Beijing- based tech company, infected more than 250 million computers outside China in one year, which generated 80 million yuan (USD 11.85 million) for the company, state-run The Beijing News reported.
"The nine-persons arrested are the key staff members of the company. They are all very young and have IT backgrounds. They also know something about counter-detection," said police in Haidian district of the city.
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"Simply put, the malware is activated on the links they are hidden in, unknown to the user, to increase advertisement views and, therefore, advertisement charges," the police said based on the suspects' confessions.
"The malware may take the user to certain sites against their will, which may collect their personal information. China, as a member of the international cyber community, is committed to cracking down of such crimes," Xie Jiangyong, associate professor at the Institute of Internet Governance and Law of Beijing University of Posts and Telecommunications, said.
By stimulating the infection process, the police got hold of the evidence and located the company.