Can you help me understand how spying through a power cord works? I read the the Nikkei Asia article but it’s light on details.

In servers, the data warehouses of the digital economy, the structure of the power supply system is more complicated than in ordinary consumer electronic devices like smartphones or notebooks. This makes it difficult to detect whether unwanted chips have been implanted in the power supply during production, cybersecurity experts said.

"If the server is compromised and the chip implanted in the power supply system is activated, the power lines could serve as a covert channel to transmit data," Philippe Lin, senior threat researcher at cybersecurity company Trend Micro, told Nikkei.

Do the power lines in the server farm/data centre connect to the internet at some point?