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ATPM 8.02
February 2002






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How To

by Gregory Tetrault,

What Do CD-ROMs Tell About You?

Macintosh Web-information sites like MacFixIt and Macintouch recently brought to light a problem that can affect anyone who burns CD-ROMs (data CDs) while using a Mac. Most volumes that can be mounted by a Macintosh (hard drives, removable disk cartridges, and CD-ROMs) contain invisible files that relate to the desktop. In OS 8 and 9, these files are “Desktop DB” and “Desktop DF.” These files are created by the Finder to keep track of applications and documents (and their icons), Finder window positions, tabbed folders, folder states, etc. They are why you can mount a disk and have your files’ icons appear immediately and have your Finder windows arranged exactly as you left them. The “Desktop DB” file also contains any Finder comments placed in a file. You can view and edit Finder comments by selecting a file and choosing the Get Info command from the File menu (Command-I shortcut).

So what’s the problem? CD-ROMs burned in Macintosh format can contain a copy of the “Desktop DB” and “Desktop DF” files from your boot drive. It turns out that many files downloaded from the Internet contain their URLs in the Finder comment field. These URLs are in your “Desktop DB” file. It also turns out that other information, including fragments of a file’s contents, can end up in the “Desktop DB” file. So, when you burn a Macintosh CD-ROM, all that information is available to whomever gets the CD. Did you visit any Web sites you don’t want someone to know about? Better take care who gets one of your CDs. Also, because the desktop files contain Finder Type and Creator codes, a person can determine what software you have installed.

How can someone get information from those invisible desktop files? There are many utilities that allow you to find invisible files and change their status to visible. I use a very old one called DiskTools. To see what’s in your desktop files I recommend finding and copying the “Desktop DB” file. Make the copy visible. You can then look at the text content of the “Desktop DB” file by using a utility like Can Opener or a text editor like BBEdit. Here’s a fragment of my “Desktop DB” file:

Dialog Dumpert Builderlper
DarkSideDecoderBuilderlperDarkSideDecoderBuilderlper TechTool® Pro
.jpg mfdrFNDR mfdrFNDR mfdrFNDR mfdrFNDRmfdraear mfdraear mfdraear
mfdraear mfdraear mfdraear mfdraedb mfdraedbmfdraedb mfdraedb mfdraedb
mfdraedb mfdraedb mfdraedb mfdraedb mfdraedbCDSpinDoctornet Accessgant
CD Spin Doctort Accessgant SimpleSoundtortAccessgant nh  

So, what can you tell from this fragment? I have installed MPEG2 Decoder which can extract clips from MPEG2 movies such as those contained on DVDs. I downloaded numerous JPEG photos from the Web site. (That was months ago!) I have installed CD Spin Doctor (a part of Toast 5 Titanium), Simple Sound, and Scrapbook. Other information in my desktop file included the titles of articles I read online and the creator codes of all my applications. Distributing this information on a CD-ROM is not a good thing.

Why does this happen? As I mentioned, bootable volumes must have these invisible desktop files. If you burn a Macintosh CD-ROM by selecting files in Roxio’s Toast or Apple Computer’s CD Burner, the application copies the “Desktop DB” and “Desktop DF” files from your startup drive. This seems like a bug, but one can argue that it is a feature. By installing the desktop files from your startup drive, if you boot up from that CD its Finder will know all your applications and their file types and also retain all your files’ Finder comments. Personally, I think Apple should have generic desktop files for burning CDs. These generic files would contain common File Type and Creator codes but no private information from you. Since OS 9 is on its way to becoming orphan technology, I doubt Apple will make such a change.

How can you avoid sending out your desktop files? Many suggestions have been made about this. Here are some options:

1. Burn only ISO 9660-formatted CD-ROMs. These disks do not contain desktop files. However, they are not bootable and do not behave like normal Macintosh volumes.

2. Purge your desktop files prior to burning CD-ROMs. This can eliminate Web-site information from your desktop files at the cost of losing all Finder comments. You can do this easily by using a utility like Micromat’s TechTool Lite which discards your desktop files (do not save Finder comments) and rebuilds them. Then, when you burn a CD-ROM it will contain a boring “Desktop DB” file. However, the desktop file will still have information on all your installed applications.


Disk Copy Image Creation Dialog Box

3. Do not burn CD-ROMs directly. Instead, use Apple’s Disk Copy (or Roxio’s Toast) to make a disk image large enough to hold your CD files. Make sure the “Mount Image” option is checked. The new empty image file mounts on your desktop. The “Desktop DB” file for your new image contains only the following: “atcoatco.” Copy the files for your CD onto this new image disk. Burn your new CD from this image and it will have essentially empty desktop files.

Remember that none of these options is necessary when burning audio CDs, ISO 9660 CDs, MPEG CDs, or video CDs. None of these generic formats will contain Mac OS desktop files.

I prefer option three since it provides the most flexibility. You can burn Mac-formatted CD-ROMs, you can retain your Finder comments, you don’t have to rebuild your desktop, and you can use any available CD-burning software.

So remember, burn securely if you plan to distribute your CD-ROM.

Challenge Followup

Last month in my How To column, Working with Downloaded Files without Special Utilities, I gave our readers a challenge. I asked readers to send me downloadable files (or their URLs) that might be difficult to open. I promised that persons who sent me an unadulterated file I could not open without resorting to ResEdit would win a prize.

Apparently, the challenge was too much. I received a grand total of 0 contest entries! I will leave the challenge open for another month, although I frankly do not expect any winner. Todd Blanchard, the originator of the “Mac OS X Anti Metadata Petition,” never met my challenge, either, even though he claimed that he and one of his relatives often downloaded files that needed ResEdit changes before being usable.

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Reader Comments (6)

anonymous · February 3, 2002 - 04:02 EST #1
Very useful, thank you.
Don Shapeno · February 3, 2002 - 15:59 EST #2
Very helpful!

I'd love to have similar info, but related to how I can burn a bootable CD that has my own operating system on it. It's easy to burn a CD, but what does one have to do in order to make it bootable?

Michael Tsai (ATPM Staff) · February 3, 2002 - 16:17 EST #3
You need to put valid system software on the CD, and then use a utility like Toast that has a checkbox for making the CD bootable.

If you're using OS X, BootCD is helpful for the former.
Tom McCarty · March 6, 2002 - 16:56 EST #4
Check MacWorld's archives. Great article on how to do it. Also, put on TTool. What you need to do is use the Mac's disk image tool, then add the OS and other software to the image or cache open the app in cache, and do the registration to activate it so it will work on the closed CD. Same for Disk Warrior or anything you want to be working on the boot system. If this doesn't make sense, it will in the article. And Toast for OS X is now available free to registered users.
Harry Stergis · April 24, 2002 - 04:03 EST #5
WOW! Who knew that Apples included all this information on burned CDs!
Harry Nygaard · April 11, 2003 - 17:41 EST #6
I can make a bootable disk on an external Zip disk. In fact, I've added Disk Doctor to it as a bootable repair disk. I use OS 9.2.2 and have found that Disc Burner 1.0.2 will unbless a bootable disc image during the burn process. How do I get around this without buying Toast?


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