Chip-level security for IoT devices is achieved by implementing security measures directly into the hardware, such as secure boot, secure firmware updates, and device authentication. This involves storing cryptographic keys in a tamper-resistant environment within the chip, ensuring that sensitive information remains secure even in the event of physical attacks on the device. Closing insecure network services is part of a broader security strategy that includes chip-level measures to protect against cyberattacks. It's important to note that while changing passwords and encrypting interfaces are also security measures, they do not pertain specifically to chip-level security.