: In the STEP 7-Micro/WIN SMART software, navigate to the PLC menu and select Clear .

Before resorting to third-party tools, try the official channel. If you are the legal end-user, Siemens offers a password removal service. This is the safest "unlock work" but requires paperwork.

: Use a Siemens PPI or MPI adapter cable for RS485 connections.

If you need a peer-reviewed or university-published style of analysis regarding Siemens PLC vulnerabilities: Vulnerability Analysis of S7 PLCs (Queen's University Belfast).