Which country recently was alleged of breaking into the system of high value of many nations?

China has been alleged by multiple nations and cybersecurity firms to be behind systematic cyber espionage campaigns targeting high-value systems across government, military, and corporate sectors worldwide. Operations like 'Cloud Hopper' and numerous APT (Advanced Persistent Threat) groups attributed to China have been accused of stealing intellectual property and trade secrets from numerous countries. While Russia and North Korea are also major cyber actors, the question refers to China's broad-based economic espionage campaigns.