The United Kingdom's cyber security agency has reported a sharp rise in serious online attacks, attributing much of the threat to hackers linked to China and Russia. In its latest annual review, the agency highlighted a fifty percent increase in highly significant incidents over the past year, with attacks affecting major companies and critical infrastructure. The report warns that hostile states and criminal groups are using advanced techniques, including artificial intelligence, to target a wide range of sectors. Officials are urging businesses to strengthen their cyber defences as the gap between threats and national resilience continues to grow.