Chinese spies used a tiny microchip to hack some of America’s top companies, including Apple and Amazon, Bloomberg Business reports. A top-secret U.S. probe into the hack allegedly found that the attackers were able to use the hardware to create a doorway into any network that included the microchips. Unlike software-based attacks, Bloomberg writes that “hardware hacks are more difficult to pull off and potentially more devastating.” Joe Grand, a hardware hacker and founder of Grand Idea Studio Inc., told the magazine that “having a well-done, nation-state-level hardware implant surface would be like witnessing a unicorn jumping over a rainbow.” Amazon and Apple both dispute aspects of Bloomberg’s reporting. “Apple has never found malicious chips, ‘hardware manipulations’ or vulnerabilities purposely planted in any server,” the company wrote. Meanwhile, according to the magazine, the companies’ denials were contradicted by six current and former senior national-security officials.