In a confidential letter to 300 major UK firms including corporate law firms and accountants the head of MI5 has warned that Chinese state agents are likely to be probing their computer systems for weaknesses that could be exploited for espionage purposes.

Internet espionage is nothing new but the letter reflects a new level of official concern, and singling out China is a new departure.

Inevitably in a country that lost the confidential details of 25 million citizens last month with no obvious help from China, the MI5 letter has leaked.

Details at this link.