The victim company claims the attack took down its website for several days, causing losses of almost 10 million yuan ($1.6 million).
One of the five arrested, surnamed Wu, told police in Shanghai's Xuhui District that he had been hired by a competing firm to attack the company.
The group allegedly compromised several computers owned by schools and enterprises, then leveraged the compromised machines to launch a DDoS attack that took down the login page for the victim's website, making it inaccessible to customers.
The other four arrested include the owner of the competing company that hired Wu, and three members of Wu's hacker group.
All five are now in detention or awaiting trial.
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