Section: User Commands (1)
Updated: JAN 2005
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sorter - Sort files in an image into categories based on file type
[-e] [-E] [-h] [-l] [-md5] [-s] [-sha1] [-U] [-v] [-V] [-a
] [-i imgtype] [-o imgoffset] [-f fstype] image [image] [meta_addr]
is a Perl script that analyzes a file system to organize the
allocated and unallocated files by file type. It runs the 'file'
command on each file and organizes the files according to the rules
in configuration files. Extension mismatching is also done to
identify 'hidden' files. One can also provide hash databases for
files that are known to be good and can be ignored and files that are
known to be bad and should be alerted.
By default, the program uses the configuration files in the directory
where The Sleuth Kit was installed. Those can be overruled with
run-time options. There is a standard configuration file for all
file system types and then a specific one for a given operating
The required arguments are as follows. This will analyze one or more
images and either save the results in the '-d' directory or list
the results to STDOUT (if '-l' is given).
- -d dir
Specify the location of where all files should be written. This includes
the index files and subdirectories if the '-s' flag is given.
This MUST be given, unless the '-l' list flag is given.
List information to STDOUT (no files are ever written). This is useful
for Incident Response, with the use of 'netcat'. This cannot be used
if '-d' is used.
The file names of the image(s) to analyze.
The options are as follows:
- -f fstype
Specify the file system type of the image(s). This is the same
type that The Sleuth Kit uses.
- -i imgtype
Specify the image type in which the file system is located. This
is the same type that The Sleuth Kit uses.
- -o imgoffset
Specify the sector offset from the beginning of the image to the start of the file system.
- -c config
Specify the location of an additional configuration file. This file
will be loaded in addition to the standard ones in the install directory.
These settings will
have priority over the standard files.
- -C config
Specify the location of the ONLY configuration file. The standard config
files will not be loaded if this option is given. For example, in the
'share/sort' directory there is a file called 'images.sort'. This file
contains only rules about graphic images. If it is specified with -C, then
only images will be saved about the image.
- -m mnt
Specify the mounting point of the image being analyzed. This is only
for cosmetic reasons. When the entries in the output files are written,
the files will have a the full path instead of just the relative path.
If this is given, then only one image can be
- -a hash_alert
Specify the location a hash database with entries of known 'bad' files.
If any file is found with an MD5 hash value in this database, it will
be placed in a special alert file. This database must have been
indexed for MD5 using 'hfind' in The Sleuth Kit before it is used by sorter.
- -n nsrl_db
Specify the location of the NIST National Software Reference Library
(NSRL) database (www.nsrl.nist.org). Any file found in the NSRL
will be ignored and not placed into a category. The database must
be indexed for MD5 with 'hfind' in The Sleuth Kit before it is used by sorter.
The database file is currently called 'NSRLFile.txt'.
- -x hash_exclude
Specify the location a hash database with entries of known 'good'
files. If any file is found with an MD5 hash value in this database,
it will be ignored and not processed or saved to the category files.
This database must have been indexed for MD5 using 'hfind' in The Sleuth Kit before
it is used by sorter.
Perform extension mismatch checks on (no category index files are generated)
Perform category indexing only (no extension mismatch checks)
Do no save data about unknown file types. By default, an 'unknown'
file is created for files where the 'file' output is not known. This allows
one to refine their configuration. If this is not desired, use this flag.
Create category files in HTML
Calculate the MD5 value for each file and save it in the category file.
This will be done automatically when any of the databases are given.
Calculate the SHA-1 value for each file and save it in the category file.
Save the actual file content to sub-directories in the directory
specified by '-d'. For example, all JPG and GIF files would actually be
saved in the 'images' directory. If '-h' is also given, thumbnails of
graphic images are also created.
Display verbose information
The meta data address of the directory to start with. By default,
the root directory is used. If this is given, then only one image
can be given.
HIGH-LEVEL OVERVIEW OF PROCESS
is a Perl script that interacts with other The Sleuth Kit tools. It starts
by reading the configuration files from the installation directory.
There is a general configuration file and a specific one for each
operating system. The specific one is determined from the '-f'
flag. Each configuration file contains rules for processing the
output of the 'file' command. One type of line identifies which
category (i.e. 'images') a given 'file' output belongs to (i.e.
'image data') (using regular expressions). Another rule shows the
file extensions (i.e. .txt) that belong to a 'file' output (i.e.
ASCII(.*?)text). See the Rules section below.
The program then runs the 'fls' tool in The Sleuth Kit to identify the files
in the file system image. Each identified file is viewed using
the 'icat' tool. If a hash database is given, the hash of the file is
calculated and looked up. If it is found in an 'alert' database,
then it is added to a special 'alert.txt' file. If it is found in
the NSRL or 'exclude' database, then it is ignored as a known good
file. Excluded files are recorded in an 'exclude' file for future
reference but it is not saved in the category files.
The 'file' command is then run to identify the file type (based on
The configuration file rules are used to identify which category
it belongs to. An entry is added to the corresponding category
file (in the '-d dir' directory). If the '-s' flag is given, then
a copy of the file is saved in a subdirectory of the same name as
the category. If the HTML format is used, then hyper-links will
allow one to easily view saved files and view what is in each
Files that do not have a category are recorded in the 'unknown'
category and the 'data' category. 'data' is for files with a
structure that 'file' does not know and 'unknown' is for files with
a structure that 'file' knows about. These are saved for future
reference, but the unknown category can be ignored by using
the '-U' flag.
A copy of the files can be saved by using the '-s' flag. If so,
then the files are saved in a subdirectory that is named with
the category name. Each file is named using the file system image
name followed by the meta data address and the original file
extension. The category index file can be used to translate the
actual name to the saved name. The HTML format makes viewing easier
as there are links to each file from the category index file.
The program will also consult the rules about the file extension.
If the file has an extension at the end of it (anything after a
found in the rules as a valid extension for the file type, it will
be added to the file of 'mismatch'. If the file does not have an
extension it will not be entered even if the file type has valid
extensions. This check is done even if the file is found in one
of the known good hash databases. If it is found in one of those,
it will be added to a special file. Files of type 'data' have
no extension checks done by default (as they have an unknown
The program repeats the above procedures using the output of the 'ils'
command as well. This allows 'sorter' to examine the contents of
unallocated files that still have pointers to the data units (not all
file systems will produce data from this step).
Configuration files are used to define what file types belong in which
categories and what extensions belong to what file types. Configuration
files are distributed with the 'sorter' tool and are located in the
installation directory in the 'share/sorter' directory.
The 'default.sort' file is used by any file system type. It contains
entries for common file types. A specific operating system file also
exists, which is useful for extensions that are specific to a given OS.
By default, the default file and the OS specific one will be used. Using
the '-c' flag, an additional file can be used. If the '-C' flag is used,
then only the supplied configuration file is used.
There are two rule types in the configuration files. Each rule starts
with a header that specifies which rule type it is (category or ext).
Both rule types have two additional columns that can be separated by
any white space.
The category rule has the category name as the second column and a
Perl regular expression in the third column. The category name can
not have any spaces in it and can only be letters and numbers.
The regular expression
is used to examine the output of 'file'. The regular expression will
be used case insensitive. More than one rule can exist for
a category, but only one category can exist for a given file output.
This saves all file output with 'image data' anywhere in it to the
category images image data
This saves all file output that has 'ASCII' followed by anything and
then 'text' to be saved to the 'text' category:
category text ASCII(.*?)text
This saves all file output that is just 'data' to the 'data' category
(the ^ and $ define the boundaries in Perl). The 'data' value is
common in the output of file for unknown binary data.
category data ^data?
There is a special category of 'ignore' that is used to skip over
files of this type. This is mainly a time and space saver.
The extension rule is similar except that the second column has the
value extensions for the file output. Multiple rules can exist for
the same file type. The comparison will be done case insensitive.
If no extension is valid for the file type, a rule does not need to
be made. That is already assumed.
For example, the ASCII is used for several file extensions so the
following rules could exist:
ext txt,log ASCII(.*?)text
ext c,cpp,h,js ASCII(.*?)text
Please email me any rules that you find useful for standard investigations
and I will incorporate them into future releases (firstname.lastname@example.org).
To run sorter with no hash databases, the following can be used:
# sorter -f ntfs -d data/sorter images/hda1.dd
# sorter -d data/sorter images/hda1.dd
# sorter -i raw -f ntfs -o 63 -d data/sorter images/hda.dd
To include the NSRL, an exclude, and an alert hash database:
# sorter -f ntfs -d data/sorter -a /usr/hash/rootkit.db -x /usr/hash/win2k.db -n /usr/hash/nsrl/NSRLFile.txt images/hda1.dd
To just identify images using the supplied 'images.sort' file:
# sorter -f ntfs -C /usr/local/sleuthkit/share/sort/images.sort -d data/sorter -h -s images/hda1.dd
The NIST National Software Reference Library (NSRL) can be found at
Distributed under the Common Public License, found in the
file in the The Sleuth Kit licenses directory.
sorter first appeared in TASK 1.52.
Brian Carrier <email@example.com>
- HIGH-LEVEL OVERVIEW OF PROCESS
- CONFIGURATION FILES
linux.jgfs.net manual pages