OPC represents an easy to use, ubiquitous, reliable method of communication. As a result of it being based on DCOM; it is well known by security professionals, but unfortunately is also known by virus writers and hackers. Layers of security mean that should one part of the system be compromised, the rest will remain secure. Typical layers used include: physical business layer security, physical process layer security, exposure to the internet, business to process layer traversal, OPC architecture security, DCOM configuration, login security, firewalls, etc.
Matrikon (2007) Creating Secure OPC Architectures