A method for preventing a dirty virtual machine from executing on an undesirable host server includes receiving, by a caching module provided for a first host server that hosts a virtual machine, a write data that is of the virtual machine and that is to be cached for the first host server. The virtual machine uses a virtual hard disk supporting hyper-V Virtual hard disk (VHDX) and virtual hard disk (VHD) file formats or any virtual file format with uniquely identifiable metadata. In response to the receipt of write data, the caching module provided for the first host server changes metadata of virtual hard disk files to a custom format before the virtual machine migrates from the first host server to a second host server, and the virtual machine becomes dirty as a result. When the dirty virtual machine sends a migration request to the second host server, a caching module provided for the second host server checks whether the custom format of the virtual hard disk files is identifiable. If not, then the second host server rejects the migration request initiated by the virtual machine.