A firmware reflash is the process of replacing a device’s firmware or system image with a clean, trusted version. Firmware sits below the operating system and may control boot behavior, hardware initialization, and core device functions. Because it loads early and can persist across reboots, malware embedded in firmware or a system partition can survive ordinary app removal and factory resets.
In cyber security, reflashing is a common recovery step after supply-chain tampering, malicious preloads, or boot-level compromise. It can restore a phone, router, or embedded device to a known-good state, but only if the replacement image comes from a verified source and the flashing process itself is protected. On locked or signed devices, defenders may also need bootloader unlocking, vendor tools, or verified boot checks to confirm the new image has not been altered again.