Older methods involved downgrading firmware to V1.0, exploiting buffer overflows. This is —it fails on modern firmware.
When a Level 3 or 4 password is lost, the standard recovery option is a factory reset via a memory cartridge or MicroWIN PLC -> Clear. However, this erases the user program. A "fixed unlock" implies restoring access without data loss. siemens s7 200 smart password unlock fixed
When the original program must be recovered from the PLC but the password is lost, industrial automation specialists rely on specialized EEPROM or flash memory manipulation. Older methods involved downgrading firmware to V1