Police in Vietnam have arrested 20 people for stealing and taking control of tens of thousands of Facebook accounts both domestically and internationally, state media said Wednesday, netting them nearly $4 million in profit.

The group is accused of producing and spreading malware to hijack more than 25,000 high-value business accounts, according to VNExpress.

Cybersecurity police made the arrests during several raids across Hanoi, business hub Ho Chi Minh City and northern Nam Dinh province in April.

The group is believed to be headed by 31-year-old Dang Dinh Son who had purchased a $1,200-malware source to steal Facebook user account information.

The man from Nam Dinh province used this malware to take control of two popular Facebook fan pages related to two photo editing sites — “Art Bay AI” and “Evoto Studio”, state media said.

They then lured Facebook users to download and install an application whose malware would infiltrate users’ devices.

Stolen data was collected and transmitted back to a server controlled by Son and then distributed to five groups on Telegram to allow his team members to hijack user accounts.

The high-value Facebook accounts were sold for profit by the gang. Other accounts of lower value were used to run advertisements for selling clothing and other items on e-commerce platforms.

The accused reportedly pocketed $3.8 million.

As of April, Vietnam ranked 7th in the world in terms of total number of Facebook users — 75.3 million — according to Statista.