by: George Starcher, Associate Editor

I was catching up on Pauldotcom Security Weekly podcast episodes. Larry covered a nice tool on modifying and even scrubbing exif tags in image files. Exif is the Exchangeable image file format. You can read more on it over on Wikipedia (exif). But in essence a lot of information can be stored in the tags within images that you take with today’s digital devices and tools. If you listen to the episode of Pauldot Larry covers some history where a hacker’s identity was exposed by exif image information in PDC Episode 92.

Larry talked about ExifTool by Phil Harvey. A great command line tool that can modify the exif information. It can even clear it all out in one shot. Well for typical mac users I checked out the tool. And here is how you make an Automator action to scrub the exif data from any images you select. I will plan to do another post later making this into an AppleScript folder action. Then you’ll be able to just scrub images by dropping them into a dedicated folder.

Here is what you do:

1. Download and install ExifTool by Phil Harvey. there is a OSX DMG with an installer.
2. Open Automator: Add the Ask for Finder Items action, then the run Shell Script action.
3. Here is the text you need to paste into the script text box:
   

   for f in “$@”
   do
   cd `dirname “$f”`
   name=`basename “$f”`
   exiftool -All= $name
   done

4. Here is a screen shot of the Automator action:

   
   Uploaded with plasq‘s Skitch!

So that is all you have to do to set it up. Now all you have to do is run the automator, select the desired images and the exiftool will scrub the images. It will also rename a copy of each image adding _original to the filename of the copy.

Here is an example of before and after exif information for one of my images.

• Before Exif:
  

  ExifTool Version Number : 7.08
  File Name : IMG_2443.jpg
  Directory : .
  File Size : 1444 kB
  File Modification Date/Time : 2007:12:29 19:31:01
  File Type : JPEG
  MIME Type : image/jpeg
  JFIF Version : 1.2
  Exif Byte Order : Big-endian (Motorola)
  Software : Adobe Photoshop Elements 4.0.1 Macintosh
  Host Computer : Mac OS X 10.5.1
  Flash : Auto, Fired, Red-eye reduction
  User Comment :
  Compression : JPEG (old-style)
  Thumbnail Offset : 1140
  Thumbnail Length : 4447
  Displayed Units X : inches
  Displayed Units Y : inches
  Global Angle : 30
  Global Altitude : 30
  Copyright Flag : False
  Photoshop Thumbnail : (Binary data 4447 bytes, use -b option to extract)
  Photoshop Quality : 12
  Photoshop Format : Standard
  Progressive Scans : 3 Scans
  Orientation : Horizontal (normal)
  Y Cb Cr Positioning : Centered
  X Resolution : 72
  Y Resolution : 72
  Resolution Unit : inches
  Make : Canon
  Camera Model Name : Canon PowerShot S2 IS
  Modify Date : 2007:12:29 19:30:59-06:00
  Creator Tool : Adobe Photoshop Elements 4.0.1 Macintosh
  Create Date : 2007:12:25 10:19:38-06:00
  Metadata Date : 2007:12:29 19:30:59-06:00
  Exif Version : 0220
  Flashpix Version : 0100
  Color Space : Unknown (-1)
  Components Configuration : Y, Cb, Cr, .
  Compressed Bits Per Pixel : 5
  Exif Image Width : 2048
  Exif Image Height : 1536
  Date/Time Original : 2007:12:25 10:19:38-06:00
  Date/Time Digitized : 2007:12:25 10:19:38-06:00
  Exposure Time : 1/60
  F Number : 3.5
  Shutter Speed Value : 1/60
  Aperture Value : 3.5
  Exposure Compensation : 0
  Max Aperture Value : 3.5
  Metering Mode : Center-weighted average
  Flash Fired : True
  Flash Return : No return detection
  Flash Mode : Auto
  Flash Function : False
  Flash Red Eye Mode : True
  Focal Length : 45.2mm
  Focal Plane X Resolution : 9102.22222222222
  Focal Plane Y Resolution : 9142.85714285714
  Focal Plane Resolution Unit : inches
  Sensing Method : One-chip color area
  File Source : Digital Camera
  Custom Rendered : Normal
  Exposure Mode : Auto
  White Balance : Manual
  Digital Zoom Ratio : 1
  Scene Capture Type : Standard
  Native Digest : 36864,40960,40961,37121,37122,40962,40963,37510,40964,36867,36868,33434,33437,34850,34852,34855,34856,37377,37378,37379,37380,37381,37382,37383,37384,37385,37386,37396,41483,41484,41486,41487,41488,41492,41493,41495,41728,41729,41730,41985,41986,41987,41988,41989,41990,41991,41992,41993,41994,41995,41996,42016,0,2,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,20,22,23,24,25,26,27,28,30;E2FE07EC68065108BEEC985345A86187
  Document ID : uuid:DF64CDADB7D511DCA426BF8A1828634F
  Instance ID : uuid:DF64CDAFB7D511DCA426BF8A1828634F
  Format : image/jpeg
  Color Mode : 3
  ICC Profile Name : Camera RGB Profile
  History :
  Profile CMM Type : appl
  Profile Version : 2.2.0
  Profile Class : Input Device Profile
  Color Space Data : RGB
  Profile Connection Space : XYZ
  Profile Date Time : 2003:07:01 00:00:00
  Profile File Signature : acsp
  Primary Platform : Apple Computer Inc.
  CMM Flags : Not Embedded, Independent
  Device Manufacturer : appl
  Device Model :
  Device Attributes : Reflective, Glossy, Positive, Color
  Rendering Intent : Perceptual
  Connection Space Illuminant : 0.9642 1 0.82491
  Profile Creator : appl
  Profile ID : 0
  Red Matrix Column : 0.45427 0.24263 0.01482
  Green Matrix Column : 0.35332 0.67441 0.09042
  Blue Matrix Column : 0.15662 0.08336 0.71953
  Media White Point : 0.95047 1 1.0891
  Chromatic Adaptation : 1.04788 0.02292 -0.0502 0.02957 0.99049 -0.01706 -0.00923 0.01508 0.75165
  Red Tone Reproduction Curve : (Binary data 14 bytes, use -b option to extract)
  Green Tone Reproduction Curve : (Binary data 14 bytes, use -b option to extract)
  Blue Tone Reproduction Curve : (Binary data 14 bytes, use -b option to extract)
  Profile Description : Camera RGB Profile
  Profile Copyright : Copyright 2003 Apple Computer Inc., all rights reserved.
  Profile Description ML : Camera RGB Profile
  DCT Encode Version : 100
  APP14 Flags 0 : [14]
  APP14 Flags 1 : (none)
  Color Transform : YCbCr
  Image Width : 2048
  Image Height : 1536
  Encoding Process : Baseline DCT, Huffman coding
  Bits Per Sample : 8
  Color Components : 3
  Y Cb Cr Sub Sampling : YCbCr4:4:4 (1 1)
  Aperture : 3.5
  Image Size : 2048×1536
  Scale Factor To 35mm Equivalent : 6.1
  Shutter Speed : 1/60
  Thumbnail Image : (Binary data 4447 bytes, use -b option to extract)
  Circle Of Confusion : 0.005 mm
  Field Of View : 7.5 deg
  Focal Length : 45.2mm (35mm equivalent: 274.2mm)
  Hyperfocal Distance : 117.85 m

• After Exif:
  

  ExifTool Version Number : 7.08
  File Name : IMG_2443.jpg
  Directory : .
  File Size : 1408 kB
  File Modification Date/Time : 2008:01:06 12:11:12
  File Type : JPEG
  MIME Type : image/jpeg
  Image Width : 2048
  Image Height : 1536
  Encoding Process : Baseline DCT, Huffman coding
  Bits Per Sample : 8
  Color Components : 3
  Y Cb Cr Sub Sampling : YCbCr4:4:4 (1 1)
  Image Size : 2048×1536

Enjoy!