CodeGuard keeps a backup of your site on our servers. Then, we use standard open protocols (FTP and SFTP) to monitor your site and check for changes. If anything has changed from the backup we have on file, we take a new backup and notify you by e-mail.
If you ever want to go back to a previous version of your site, just use CodeGuard's restoration functionality to choose the backup you want to revert to.
Want more details? Check out more on How CodeGuard Works.