China’s top spy agency has issued a rare warning on espionage risks inside the country. On Tuesday, China’s Ministry of State Security (MSS) disclosed a range of advanced surveillance techniques, cautioning that even high-security meetings are increasingly vulnerable to remote monitoring and interception.
According to the disclosure by MSS, modern optical tools including high-resolution telephoto lenses, infrared imaging devices and AI-enhanced smartphones can capture documents, presentation slides and whiteboard content from hundreds of metres away.
The MSS also highlighted the growing threat of laser-based eavesdropping. Sound waves inside a room can cause minute vibrations in window glass. By directing an invisible laser beam at the surface and analysing the reflected signals, external actors can reconstruct conversations without physically entering the space.
Authorities further warned that everyday objects including whiteboards, screens, eyeglasses and watches can act as reflective surfaces. Using high-powered optical equipment from nearby buildings, spies can capture these reflections and reconstruct sensitive information. The risk is particularly acute at night, when brightly lit interiors make windows appear almost transparent from outside.
To counter such threats, the MSS advised that sensitive meetings should ideally be held in interior rooms without windows. Where windows are unavoidable, measures such as blackout curtains, privacy films or smart glass should be used. Additional safeguards include regular inspections of surrounding areas, electromagnetic shielding to block wireless signals, and the use of audio interference and laser detection systems.
The agency also urged vigilance, advising that any suspected leaks or suspicious activity be reported through official national security channels, including the 12339 hotline.
The warning comes against the backdrop of a widening anti-corruption campaign under President Xi Jinping that has increasingly targeted China’s military and scientific elite.
Last week, the profiles of at least three of China’s leading nuclear, missile and radar experts were removed from the website of the Chinese Academy of Engineering, the country’s most prestigious academic body.
The move has fuelled speculation that the ongoing purge which has already shaken the upper ranks of the People’s Liberation Army (PLA) is now extending into academia.
