A guest-transparent file integrity monitoring method in virtualization environment

The file system becomes the usual target of malicious attacks because it contains lots of sensitive data, such as executable programs, configuration and authorization information. File integrity monitoring is an effective approach to discover aggressive behavior by detecting modification actions on these sensitive files. Traditional real-time integrity monitoring tools, which insert hooks into the OS kernel, are easily controlled and disabled by malicious software. Such existing methods, which insert kernel module into OS, are hard to be compatible because of the diversity of OS. In this paper, we present a non-intrusive real-time file integrity monitoring method in virtual machine-based computing environment, which is transparent to the monitored system. The monitor is isolated from the monitored system, since it observes the state of the monitored system from the outside. This method brings two benefits: detecting file operations in real time and being invisible to malicious attackers in the monitored system. Furthermore, a kind of file classification algorithm based on file security level is proposed to improve efficiency in this paper. The proposed file integrity monitoring method is implemented in the full-virtualization mode supported by the Xen platform. The experimental results show that the method is effective with acceptable overhead.