TIANJIN -- China cracked down on 644 botnets -- networks of internet-connected devices controlled to launch cyberattacks -- in 2017, further reducing their number in the country, according to a recent report.

The report by the National Computer Network Emergency Response Technical Team showed the number of computers infected with malware in China in 2017 was around 12.56 million, down by 26.1 percent year on year.

Most of the infected computers were under control by around 32,000 malware command-and-control servers outside the Chinese mainland, with the top three number of servers located in the United States, Russia and Japan, according to the report.

The report also found there were more than 3,000 botnets with more than 100 malware-infected bots and 32 botnets with more than 100,000 malware-infected bots in China.

The number of botnet command-and-control servers in the Chinese mainland has been decreasing steadily in recent years, according to cybersecurity company Kaspersky.