Legacy Factory System Rebuilt Without Source Code

From outdated black-box software to a fully functional, scalable factory control platform

How we recovered a legacy factory system without source code by applying reverse engineering legacy software, hardware integration, and modern architecture delivery to achieve full factory control system modernization.

Legacy Factory System Rebuilt Without Source Code

Client’s Background

The client is a mid-sized manufacturing company based in the USA, New York. Their production lines relied on an aging factory control system that had been developed more than 15 years ago. The system resembled a SCADA environment but had been heavily customized over the years. Crucially, the client did not have access to the source code or any technical documentation.

The software issues were serious: the legacy factory system was already out of support, prone to stability problems, and lacked integration with modern IT systems and end-users’ needs. Every unplanned downtime carried significant financial risk. They found ModLogix team to modernize their software to avoid financial risks due to downtimes and compliance purposes.

Key problems identified:

The system had reached end-of-life and was no longer supported.

No source code was available for modification or extension.

All technical documentation was missing.

The risk of prolonged downtime was increasing with every year.

Project Challenges

Undertaking a software rebuild without source code came with multiple technical and operational challenges:

No source code availability

All functionality had to be reconstructed through observation and reverse engineering legacy software.

Complex integration with aging controllers

Factory lines were controlled by Siemens PLCs using proprietary and undocumented communication protocols.

Undocumented data exchange

The team had to analyze network traffic to understand real-time communication.

Minimal production downtime

Our client could only afford very short maintenance windows, meaning deployment had to be staged and heavily validated.

Future-proof architecture

The replacement system needed to support scalability, modularity, and cloud integration in the future.

Our Solution

We designed a multi-step solution centered on factory software re-engineering and system interoperability with existing hardware. All was done using phased migration approach – to minimize any downtime.

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Reverse Engineering via Traffic and Interfaces

Using Wireshark and custom analyzers, our professional team captured and decoded communication flows between the old software and PLCs. This approach allowed us to reconstruct command structures, I/O mapping, and timing sequences without the original source code.

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