The New York Times says powerful Chinese hackers had quite a romp deep inside its computer systems. The extensive and sophisticated digital strikes came after the Times’ October report on business deals involving the family of China’s prime minister.

A detailed account of the intrusions was published by the Times. The publication says they hired a private company to track the activity of the hackers, allowing the intruders to work within the Times’ system for weeks while the attacks were being traced.

The antivirus software used by The New York Times is also popular with other companies and tens of millions of Americans, yet it missed dozens of the hacking attacks.

Damian Grammaticas, a BBC correspondent based in Beijing, says working as a journalist in China takes extra precaution. “You need to be very cautious about any sort of compromised email that might try to seek to install this sort of spying software on to our systems.”

Chinese hackers are also believed to have attacked American companies, government agencies, and the military.