Evolving business models are progressively reshaping the scope and structure of ICT services, with massive introduction of virtualization paradigms and tight integration with the physical environment. Several market forces are already driving towards the creation of multi-domain and complex business service chains, which undoubtedly bring more agility in service deployment and operation but introduce additional security and privacy concerns that have not been addressed in a satisfactory way yet. Tackling conflicting trends in the cybersecurity market, like fragmentation or vendor lock-ins, GUARD will develop an open and extensible platform for advanced assurance and protection of trustworthy and reliable business chains spanning multiple administrative domains and heterogeneous infrastructures. The purpose of GUARD is manifold: i) to increase the information base for analysis and detection, while preserving privacy, ii) to improve the detection capability by data correlation between domains and sources, iii) to verify reliability and dependability by formal methods that take into account configuration and trust properties of the whole chain, and iv) to increase awareness by better propagation of knowledge to the humans in the loop. The distinctive approach of GUARD will be the architectural separation between analysis and data sources, mediated by proper abstraction; this paradigm will result in an open, modular, pluggable, extendable, and scalable security framework. This holistic solution will blend security-by-design with enhanced inspection and detection techniques, raising situational awareness at different levels of the companies’ structure by tailored informative contents, so to enable quick and effective reaction to cyber-threats. Demonstration and validation in two challenging scenarios is envisioned to bring the technology to an acceptable level of maturity, as well as direct involvement of relevant stakeholders for concrete business planning.