Security or system management software is essential for keeping systems secure. If these essential services are stopped or disabled by attackers, damages to the system increase. Therefore, protecting essential services is crucial for preventing and mitigating attacks. To deter attacks on essential services, hiding information related to essential services is helpful. This paper describes design and implementation of a method to make files invisible to all services except their corresponding essential services and provides access methods to those files in a virtual machine (VM) environment. The proposed method consists of interposition and proxy execution of the system call function. In the proposed method, the virtual machine monitor (VMM) monitors system calls invoked in a protection target VM. If an essential process invokes system calls related to file manipulation, the VMM interposes the system call and collects information from the protection target VM. If the file is an essential file, the VMM requests proxy execution to the proxy VM on another VM. After proxy-execution of the system call, the proxy process returns the result to the VMM. Finally, the VMM returns the result and skips the execution of the original system call on the protection target VM. Thus, access to essential files by the essential service is skipped on the protection target VM, but the essential service can access the file content. With this mechanism, it is difficult for attackers to monitor access to essential files. In this paper, we describe the design, implementation, and evaluation of the proposed method.