A group of hackers say they breached a massive trove of security-camera data collected by Silicon Valley startup Verkada Inc., gaining access to live feeds of 150,000 surveillance cameras inside hospitals, companies, police departments, prisons and schools.

Companies whose footage was exposed include carmaker Tesla Inc. and software provider Cloudflare Inc. In addition, hackers were able to view video from inside women's health clinics, psychiatric hospitals and the offices of Verkada itself. Some of the cameras, including in hospitals, use facial-recognition technology to identify and categorize people captured on the footage. The hackers say they also have access to the full video archive of all Verkada customers.

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