Leopard is making the headlines again, but this time in a less than positive way. Users have started coming across a bug in the Leopard Finder, which can lead to significant data loss when performing move operations on files and folders.

When moving files or folders around on the same volume, all the operating system does is update the file reference to reflect the new location. This is both simple and instantaneous. However, when moving files or folders across volumes, be they local or remote, internal or external, the information is first copied to the destination and then flagged as deleted at the origin. People using the Finder to move files about under Leopard have discovered a rather nasty error, which occurs when the connection to the target volume disappears. Under normal circumstances, since the copy step of the operation was not successful, the next step of deleting the original should not take place. However, the Leopard Finder will delete the original regardless.

The problem is irrespective of the destination type and can be rather serious if a large or important amount of information is lost. The problem seems to be somewhere in the Finder, as using the Terminal to perform the same sequence of events does not result in data loss. Since the fault lies in the lack of a check for a successful copy, solving this particular bug should be very simple and it should not take Apple long to come up with a fix. In the meantime, users are encouraged to perform separate copy and delete operations on sensitive information, or when there is any risk of a connection loss.
If this bug does bite, since the original data is simply marked as 'deleted' and not actually overwritten by the operation, it should be possible to perform an 'Undo' or use data recovery software to get it back.