The latest version is release 9.605 which is backward-compatible and works with all our DVR systems (400 / 500 /51X / 600).
You can determine what version you are currently running by logging into the application and then left clicking your mouse on the small 247Security logo located in the upper left corner of the application, then left mouse click on "About dvrclient"
This will then open another window to display the release number. You can obtain the latest version of software by logging onto the 247Security FTP site. If you don't have this info, contact technical support at 866.693.7492 and we will be glad to email you the instructions.