Service-based architecture (SBA) is a profound advancement in the novel 5G Core network (5GC). Existing studies show that SBA can benefit from cloud computing to achieve extensibility, modularity, reusability, and openness. It also brings security problems (e.g., hypervisor hijacking, and malware injection). To provide secure 5G services, we propose a service-based cloud architecture called Mimicloud for 5GC based on dynamic and heterogeneous techniques. Mimicloud provides flexible reconfiguration mechanisms to protect containers and eliminate all attack knowledge obtained from adversaries. We use multiple containers to execute crucial services and ensure security with crosscheck. Mimicloud employs heterogeneous components to prevent multiple containers from being breached through the same vulnerabilities. Experimental results show that Mimicloud can effectively strengthen the security of the 5GC. The performance overhead is analyzed in order to demonstrate its scalability.