Posted by Nando:
I agree with what you’ve said from a security and development point of view, the current methods the system uses to identify the application to which a file is registered seems quite secure to me though. I’ve decided to play with some of my files, changing the extension of a .mov file to .doc, and the system would recognize it as a Quicktime movie just fine. I did that with non-apple formats, and even a document kind I created for fun, and it would open on the right application even if saved with anotehr extension.

The problem really lies within the file’s data fork, once you change that you can easily have the application open a file that is not attached to it, which might not be a succesful task. But in the case of malicious files, the icon is what really makes the confusion, as you have said on a recent post.

Custom icons are easy to apply to files, you can do it easily from Finder itself, with special applications such as IconFactory’s Pixadex or Unsanity’s Shapeshifter. The second one, as far as I know, really does play with the data forks, changing the icons from inside out, while Pixadex just applies them as a cover that is easily removable.

On either case, killing custom icons is really not a solution. First of all because it would mean a dead end to those who, like me, make a living out of that. Ask the guys from IconFactory and MacThemes Forums, they’ll probably like their Macs pretty with custom themes and icons than a “secure” one – and we know this doesn’t actually threatens anyone’s security, yet.

One thing that could work is have the software check if the icon it’s file holds is not the icon for another application’s file. The system has a list of the icons for each file type, so a background check on that wouldn’t take long at all, probably not over 0.3 seconds. If the icon is unknown, the software would ask the system “Is this a themed OS?” (something that would be set on System Preferences against Apple’s will or through Third-Party software), if it is themed, carry on with the loading, if it is not, warn the user of the possible security threat.

As complicated as this solution might sound, I don’t see any other way to keep everyone happy – and secure. So let’s just hope in 5 years the Mac is still as secure as now, it’s probably the best we can do.