accessing files from a file server

[australia3]

When we access files from a file server, users don't get a read-only prompt when someone else is using the file. They aren't set to be shared, they aren't password protected. When accessing a file in this way,users are then prompted to save as a temporary file in the same folder. This seems weird to me and din't happen previously. We don't want users to share these files just for them to be available on the server for them all to access and for them to be told when someone else is in them. Any ideas