A research report by threat intelligence experts InSights, as posted on the Cyber Security Intelligence website, describes China as "perhaps the world's greatest cyber power". That power is not being excercised for good. China has an aggressive approach to cyber operations, using them for political and national aims.
Attackers linked to China have stolen personally identifiable information, trade secrets and intellectual property, and extracted classified information from government agencies. Much of its effort is focused on foreign and domestic opponents of the Chinese Communist Party. U. S. and European targets have gotten most of the attacks, but India, Australia and specific cultural and religious groups have also been attacked.
The U. S. government has designated China as its top cyber adversary. The FBI blames China for the 2017 Equifax breach, and half of its 500,000 counterintelligence investigations are related to China. Computer users should be wary of any links to Chinese websites, or requests to connect from Chinese nationals.
During the cold war there was a saying "the optimist learns Russian; the pessimist learns Chinese". Maybe the pessimists were right.