The blog post you're likely thinking of refers to a seminal discovery in the community regarding a vulnerability in how passwords were stored on Micro Memory Cards (MMC) . On or around 11 September 2006
Use a tool like or s7ImgRd to create a raw image of the card. simatic s7 200 s7 300 mmc password unlock 2006 09 11
Because the XOR salt became known and static, the community reverse-engineered a lookup table. The unlock tool effectively re-applies that exact timestamp to the MMC, essentially rolling back the security to a state where the password algorithm is deterministic. The blog post you're likely thinking of refers
If the 2006-09-11 method fails (e.g., newer firmware), consider: The unlock tool effectively re-applies that exact timestamp
How do you reset a SIMATIC S7-300 CPU and MMC (default ... - Support
There exist third-party tools or hardware-based methods (e.g., using a card reader and direct sector editing, or using older versions of Step 7 with brute-force or backdoor techniques) that claim to reset or remove S7-200/S7-300 MMC passwords. Important warnings:
The S7-200 (e.g., CPU 221, 222, 224, 226) uses a 4-level password system: