File Juicer can search erased and corrupted flash cards for files. It does so by first making a disk image of the flash card which it then does an end to end search on. That way the card is only read once (and of course never written upon).
Hard disks can be searched the same way as flash cards, but they are much larger, the search will take much longer time and require sufficient hard drive space for the extracted files. This feature is not promoted by a specific menu in File Juicer and you will need to make a disk image of the hard drive with uncompressed read only settings. Disk Utility is excellent for this and it will even work if you plug in a PC hard disk with a firewire or USB cable. This is stressing File Juicer beyond its design and you may turn off the little checkbox (top left) for image feedback while it is running, to minimize the chance that a corrupt or fragmented file will be shown as this may cause File Juicer to quit unexpectedly. I don't promote File Juicer for hard disk recovery, as it ignores the format of the file system (be it HFS or FAT) and it will not find fragmented files.
File Juicer can do a lot of searching and it does keep some track of where the file was found to make further investigation easier.
It writes this info in Finder's "SpotLight Comments". If it can determine a download location in a browser cache file it will use this instead.
File Juicer saves two log files in your ~/Library/Logs folder. "FileJuicerLog.txt" records which files have been searched and "FileJuicerResultsLog.txt" what has been found. The results log lists several columns of information. Sample Log. The first column is the offset in bytes from the beginning of the file and the next number is the size of the found file. Then follows the type of the extracted file, its "number" counting from the beginning of the file, the file name it is extracted from (which may be a temporary file), the file which was juiced (and which may itself contain files) and lastly a checksum (used to eliminate duplicates).
File Juicer can detect compressed data embedded with the bz2 and deflate algorithms. This will save out files with the extension .inflated or .un-bzip2ed, with an offset in the file name. This will also show up in the log file as those are juiced after being decompressed. If a regular zip file is found inside, it is saved out as such, so you can decompress it manually.
When a file is extracted from inside an other file, the offset can be used to verify this with a hex editor like HexEdit. Use the "Use Decimal Addresses" in the Options menu and the "Go to address" in the Find menu to go to the offset found in the log file.
The URL files generated by File Juicer are not web pages visited, but URLs found inside any of the files dropped on File Juicer. If you drop a HTML file on File Juicer it will look for anything which looks like a URL and save it to the URL file. HTML allows for easy hiding of URLs so not everything possible is found, just what is there as plain text.
One last note about Safari's cache files: what ends up in the cache may not end there deliberately. Some web sites push content into the face of people passing by, without any clicks needed. Safari does its best to block popup windows and the like, but it will not block everything. If the web site in question is still active one can do a test visit to see if active browsing was needed.
This is the features of File Juicer i believe is most relevant for forensics, but let me know if you have more tips I should include or features you would like.Henrik Dalgaard
File Juicer was originally designed to extract images out of PowerPoint presentations and to recover photos from erased or corrupted flash cards. It has since learned to recognize a lot of file types and become a "swiss army knife" for data recovery/extraction not from hard disk images (although it can) but from files of any kind. In forensics terminology this is called "carving". Here I collect the tips and features I hear about when using File Juicer in forensics.
Many applications make low resolution images and cache files to get good performance.
iPhoto is the best example at is keeps all the images it catalogs in several resolutions ranging from tiny icons to the original untouched high resolution photo. The low resolution photos are ordinary JPEG files and directly accessible with Finder, but its icon caches are in iPhoto's private format. File Juicer can open these files and extract all the icons even for photos which have been deleted from the iPhoto library.
Safari is the most known application which caches a lot of files. It too uses its own internal format for its cache, and File Juicer can extract the images from the cache files, the same way as with iPhoto's internal cache files. Many other application (iChat, Dashboard, Mail) use Safari format cache files too, and while they are not all shown in File Juicer's menu you can drop them on File Juicer from Finder and get the images extracted the same way.
FireFox makes a cache too, and while it does not use a private file format, its cache files does not have a file extension and browsing the cache is not practical. If you let File Juicer process the cache it will make a html index file to the contents which will make it much faster to browse.
iPods and iPhones can also contain images, video and text which can be searched. You can put the iPod in "hard disk mode" with iTunes, open its folders and take a look. The most inconvenient format found in there is the ithmb file format. It is a mess of a file format and every type of iPod has its own versions of the ithmb files. I try to keep track of this and allow for conversion to tiff. The ithmb files can also be found inside the iPhoto library, but if more than one kind of iPod is used on the same Mac File Jucier many not be able to decipher them.