“In the field of cloud security, enhancing service function chain (SFC) security by composing virtual network functions (VNFs) and allocating resources considering their security attributes is crucial. Expert proposed an innovative hierarchical trust model to assess the differentiated trustworthiness among network entities caused by vulnerability correlation. Based on trustworthiness assessment, both virtual trust of VNF combinations at the SFC composition stage and physical trust of physical node (PN) selections at the SFC placement stage are globally considered to disrupt the attack chains in SFCs as much as possible. The security-aware and cost-efficient SFC composition and placement (SCSCP) problem is formulated as an integer linear programming (ILP) problem, which is NP-hard. The joint trust and cost global optimization (JTCGO) algorithm is proposed to dynamically update the trustworthiness and globally find the SFC deployment solutions including the VNF combination schemes and PN selection schemes. Simulation results demonstrate that our proposed algorithm can provide the optimal SFC deployment solutions for requests and can guarantee the SFC trustworthiness at a controllable cost, thereby protecting SFCs from network attacks in complex security environments.”