Even the most modern and sophisticated safety systems can be defeated by an attacker. This statement is validated by the discovery of malware specifically targeting safety instrumented systems (SIS), such as the
"Triton/Trisis" malware that compromised the SIS of a petrochemical plant. Safety systems, while designed as independent protection layers, are not immune to cybersecurity vulnerabilities and require specific countermeasures. Integration, such as using Modbus TCP, does not inherently reduce risk to a tolerable level without additional controls.
Reference: ISA/IEC 62443-3-3:2013, Section 4.2.2; ISA/IEC 62443-1-1:2007, Section 3.2.4; ISA/IEC 62443-
2-1:2009, Section 4.2.3.2; TRITON/TRISIS incident case studies.