Difference between pages "IDEN" and "File Carving"

From Forensics Wiki
(Difference between pages)
Jump to: navigation, search
(Wikified a bit more. Added link.)
 
m (FIle Carving Taxonomy)
 
Line 1: Line 1:
The '''Integrated Digital Enhanced Network''' ('''iDEN''') is a proprietary mobile communications technology from [[Motorola]]. It is a [[TDMA]] based digital wireless standard that operates in the 800 MHz, 900MHz, and 1.5 GHz bands. It combines the capabilities of a [[cell phones|digital cellular telephone]] and a two-way radio known as [[push-to-talk]] ([[PTT]]).
+
'''Carving''' is the practice of searching an input for files or other kinds of objects based on content, rather than on metadata. File carving is a powerful tool for recovering files and fragments of files when directory entries are corrupt or missing, as may be the case with old files that have been deleted or when performing an analysis on damaged media. Memory carving is a useful tool for analyzing physical and virtual memory dumps when the memory structures are unknown or have been overwritten.
  
Motorola’s iDEN technology phones support many other features including [[Bluetooth]], location-based services, [[MOTOTalk]] and support for expandable memory ([[Micro SD]]). [[Sprint Nextel]] is the largest U.S. retailer of iDEN services.
 
  
Newer iDEN phones use a [[SIM card]] that is compatible with [[GSM]] phones for overseas roaming but iDEN is a very different standard from GSM. iDEN phones are not compatible with GSM networks and GSM phones are not compatible with iDEN networks.
+
=File Carving=
  
== History ==
+
Most file carvers operate by looking for file headers and/or footers, and then "carving out" the blocks between these two boundaries. [[Semantic Carving]] performs carving based on an analysis of the contents of the proposed files.
  
iDEN was invented by Motorola who is presently the primary manufacturer of iDEN devices.
+
File carving should be done on a [[disk image]], rather than on the original disk.
  
Nextel has started to develop a 2.5G technology called WiDEN in order to provide high data rates for packet data. WiDEN is a planned expansion on the iDEN system, where instead of using a normal 25 kHz channel for packet data, it will encompass 4 carriers (100 kHz) into one channel. This would allow download speeds of 96 kbit/s, which is comparable to the average CDMA2000 1x speeds from American competitors Sprint and Verizon Wireless.
+
File carving tools are listed on the [[Tools:Data_Recovery]] wiki page.
  
== External Links ==
+
Many carving programs have an option to only look at or near sector boundaries where headers are found. However, searching the entire input can find files that have been embedded into other files, such as [[JPEG]]s being embedded into [[Microsoft]] [[DOC|Word documents]]. This may be considered an advantage or a disadvantage, depending on the circumstances.
  
* [http://idenphones.motorola.com/idenHome/common/what_is_iden.jsp Motorola: The iDEN Solution]
+
Today most file carving programs will only recover files that are contiguous on the media.
* [http://idenphones.motorola.com/iden/iden_home.jsp iDEN Home]
+
 
* [http://www.phoneyworld.com/newspage.aspx?n=1907 Motorola i580 iDEN]
+
== FIle Carving Taxonomy==
* [http://en.wikipedia.org/wiki/Integrated_Digital_Enhanced_Network Wikipedia: Integrated Digital Enhanced Network]
+
[[Simson Garfinkel]] and [[Joachim Metz]] have proposed the following file carving taxonomy:
 +
 
 +
;Carving
 +
:General term for extracting data (files) out of undifferentiated blocks (raw data), like "carving" a sculpture out of soap stone.
 +
 
 +
;Block Based Carving
 +
:Any carving method (algorithm) that analyzes the input on block-by-block basis to determine if a block is part of a possible output file. This method assumes that each block can only be part of a single file (or embedded file).
 +
 
 +
;Characteristic Based Carving
 +
:Any carving method (algorithm) that analyzes the input on characteristic basis (for example, entropy) to determine if the input is part of a possible output file.
 +
 
 +
;Header/Footer Carving
 +
:A method for carving files out of raw data using a distinct header (start of file marker) and footer (end of file marker).
 +
 
 +
;Header/Maximum (file) size Carving
 +
:A method for carving files out of raw data using a distinct header (start of file marker) and a maximum (file) size. This approach works because many file formats (e.g. JPEG, MP3) do not care if additional junk is appended to the end of a valid file.
 +
 
 +
;Header/Embedded Length Carving
 +
:A method for carving files out of raw data using a distinct header and a file length (size) which is embedded in the file format
 +
 
 +
;File structure based Carving
 +
:A method for carving files out of raw data using a certain level of knowledge of the internal structure of file types. Garfinkel called this approach "Semantic Carving" in his DFRWS2006 carving challenge submission, while Metz and Mora called the approach "Deep Carving."
 +
 
 +
;Semantic Carving
 +
:A method for carving files based on a linguistic analysis of the file's content. For example, a semantic carver might conclude that six blocks of french in the middle of a long HTML file written in English is a fragment left from a previous allocated file, and not from the English-language HTML file.
 +
 
 +
;Carving with Validation
 +
:A method for carving files out of raw data where the carved files are validated using a file type specific validator.
 +
 
 +
;Fragment Recovery Carving
 +
:A carving method in which two or more fragments are reassembled to form the original file or object. Garfinkel previously called this approach "Split Carving."
 +
 
 +
== File Carving challenges and test images ==
 +
 
 +
[http://www.dfrws.org/2006/challenge/]
 +
File Carving Challenge - [[Digital Forensic Research Workshop|DFRWS]] 2006
 +
 
 +
[http://dftt.sourceforge.net/test6/index.html]
 +
FAT Undelete Test #1 - Digital Forensics Tool Testing Image (dftt #6)
 +
 
 +
[http://dftt.sourceforge.net/test7/index.html]
 +
NTFS Undelete (and leap year) Test #1 - Digital Forensics Tool Testing Image (dftt #7)
 +
 
 +
[http://dftt.sourceforge.net/test11/index.html]
 +
Basic Data Carving Test - fat32 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #11)
 +
 
 +
[http://dftt.sourceforge.net/test12/index.html]
 +
Basic Data Carving Test - ext2 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #12)
 +
 
 +
==File Carving Bibliography==
 +
 
 +
Mikus, Nicholas A. "An analysis of disc carving techniques," Master's Thesis, Naval Postgraduate School. March 2005. http://handle.dtic.mil/100.2/ADA432468
 +
 
 +
Garfinkel, S., "Carving Contiguous and Fragmented Files with Fast Object Validation", (to appear at the) Digital Forensics Workshop (DFRWS 2007), Pittsburgh, PA, August 2007.  http://www.simson.net/clips/academic/2007.DFRWS.pdf
 +
 
 +
== See also ==
 +
[[Tools:Data_Recovery#Carving | FIle Carving Tools]]
 +
 
 +
=Memory Carving=

Revision as of 23:43, 11 August 2007

Carving is the practice of searching an input for files or other kinds of objects based on content, rather than on metadata. File carving is a powerful tool for recovering files and fragments of files when directory entries are corrupt or missing, as may be the case with old files that have been deleted or when performing an analysis on damaged media. Memory carving is a useful tool for analyzing physical and virtual memory dumps when the memory structures are unknown or have been overwritten.


Contents

File Carving

Most file carvers operate by looking for file headers and/or footers, and then "carving out" the blocks between these two boundaries. Semantic Carving performs carving based on an analysis of the contents of the proposed files.

File carving should be done on a disk image, rather than on the original disk.

File carving tools are listed on the Tools:Data_Recovery wiki page.

Many carving programs have an option to only look at or near sector boundaries where headers are found. However, searching the entire input can find files that have been embedded into other files, such as JPEGs being embedded into Microsoft Word documents. This may be considered an advantage or a disadvantage, depending on the circumstances.

Today most file carving programs will only recover files that are contiguous on the media.

FIle Carving Taxonomy

Simson Garfinkel and Joachim Metz have proposed the following file carving taxonomy:

Carving
General term for extracting data (files) out of undifferentiated blocks (raw data), like "carving" a sculpture out of soap stone.
Block Based Carving
Any carving method (algorithm) that analyzes the input on block-by-block basis to determine if a block is part of a possible output file. This method assumes that each block can only be part of a single file (or embedded file).
Characteristic Based Carving
Any carving method (algorithm) that analyzes the input on characteristic basis (for example, entropy) to determine if the input is part of a possible output file.
Header/Footer Carving
A method for carving files out of raw data using a distinct header (start of file marker) and footer (end of file marker).
Header/Maximum (file) size Carving
A method for carving files out of raw data using a distinct header (start of file marker) and a maximum (file) size. This approach works because many file formats (e.g. JPEG, MP3) do not care if additional junk is appended to the end of a valid file.
Header/Embedded Length Carving
A method for carving files out of raw data using a distinct header and a file length (size) which is embedded in the file format
File structure based Carving
A method for carving files out of raw data using a certain level of knowledge of the internal structure of file types. Garfinkel called this approach "Semantic Carving" in his DFRWS2006 carving challenge submission, while Metz and Mora called the approach "Deep Carving."
Semantic Carving
A method for carving files based on a linguistic analysis of the file's content. For example, a semantic carver might conclude that six blocks of french in the middle of a long HTML file written in English is a fragment left from a previous allocated file, and not from the English-language HTML file.
Carving with Validation
A method for carving files out of raw data where the carved files are validated using a file type specific validator.
Fragment Recovery Carving
A carving method in which two or more fragments are reassembled to form the original file or object. Garfinkel previously called this approach "Split Carving."

File Carving challenges and test images

[1] File Carving Challenge - DFRWS 2006

[2] FAT Undelete Test #1 - Digital Forensics Tool Testing Image (dftt #6)

[3] NTFS Undelete (and leap year) Test #1 - Digital Forensics Tool Testing Image (dftt #7)

[4] Basic Data Carving Test - fat32 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #11)

[5] Basic Data Carving Test - ext2 (by Nick Mikus) - Digital Forensics Tool Testing Image (dftt #12)

File Carving Bibliography

Mikus, Nicholas A. "An analysis of disc carving techniques," Master's Thesis, Naval Postgraduate School. March 2005. http://handle.dtic.mil/100.2/ADA432468

Garfinkel, S., "Carving Contiguous and Fragmented Files with Fast Object Validation", (to appear at the) Digital Forensics Workshop (DFRWS 2007), Pittsburgh, PA, August 2007. http://www.simson.net/clips/academic/2007.DFRWS.pdf

See also

FIle Carving Tools

Memory Carving