  While achieving security for Industrial Internet of Things (IIoT) is a
critical and non-trivial task, more attention is required for brownfield IIoT
systems. This is a consequence of long life cycles of their legacy devices
which were initially designed without considering security and IoT
connectivity, but they are now becoming more connected and integrated with
emerging IoT technologies and messaging communication protocols. Deploying
today's methodologies and solutions in brownfield IIoT systems is not viable,
as security solutions must co-exist and fit these systems requirements. This
necessitates a realistic standardized IIoT testbed that can be used as an
optimal format to measure the credibility of security solutions of IIoT
networks, analyze IIoT attack landscapes and extract threat intelligence.
Developing a testbed for brownfield IIoT systems is considered a significant
challenge as these systems are comprised of legacy, heterogeneous devices,
communication layers and applications that need to be implemented holistically
to achieve high fidelity. In this paper, we propose a new generic end-to-end
IIoT security testbed, with a particular focus on the brownfield system and
provide details of the testbed's architectural design and the implementation
process. The proposed testbed can be easily reproduced and reconfigured to
support the testing activities of new processes and various security scenarios.
The proposed testbed operation is demonstrated on different connected devices,
communication protocols and applications. The experiments demonstrate that this
testbed is effective in terms of its operation and security testing. A
comparison with existing testbeds, including a table of features is provided.
