Difference between pages "Tools:Memory Imaging" and "TDMA"

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The [[physical memory]] of computers can be imaged and analyzed using a variety of tools. Because the procedure for accessing physical memory varies between [[operating systems]], these tools are listed by operating system. Once memory has been imaged, it is subjected to [[memory analysis]] to ascertain the state of the system, extract artifacts, and so on.
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{{Wikify}}
  
One of the most vexing problems for memory imaging is verifying that the image has been created correctly.  That is, verifying that it reflects the actual contents of memory at the time of its creation. Because the contents of memory are constantly changing on a running system, the process can be repeated but the results will never--to a high degree of probability--be the same.  Thus, repeating the acquisition and comparing the results is not a feasible means of validating correct image creation.  [[Memory analysis]] can reveal whether the image's contents are consistent with the known layout and structure of a given operating system, as well as answering other questions, but it cannot answer the question as to whether the image accurately reflects the system from which it was taken at the time it was taken.
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'''TDMA - Time Division Multiple Access'''
  
== Memory Imaging Techniques ==
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TDMA (Time Division Multiple Access), has the largest network in the US.
  
; Crash Dumps
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TDMA is a digital wireless communication method allowing many users to access a single radio frequency without interference. Every individual user is given a unique time slot within each channel.
: When configured to create a full memory dump, [[Windows]] operating systems will automatically save an image of physical memory when a bugcheck (aka blue screen or kernel panic) occurs. [[Andreas Schuster]] has a [http://computer.forensikblog.de/en/2005/10/acquisition_2_crashdump.html blog post] describing this technique.
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; LiveKd Dumps
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: The [[Sysinternals]] tool [http://www.microsoft.com/technet/sysinternals/SystemInformation/LiveKd.mspx LiveKd] can be used to create an image of physical memory on a live machine in crash dump format. Once livekd is started, use the command ".dump -f [output file]"
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; Hibernation Files
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: [[Windows]] 98, 2000, XP, 2003, and Vista support a feature called [[hibernation]] that saves the machine's state to the disk when the computer is powered off. When the machine is turned on again, the state is restored and the user can return to the exact point where they left off. The machine's state, including a compressed image of [[physical memory]], is written to the disk on the system drive, usually C:, as [[hiberfil.sys]]. This file can be parsed and decompressed to obtain the memory image. Once [[hiberfil.sys]] has been obtained, [http://sandman.msuiche.net/ Sandman] can be used to convert it to a dd image.
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: [[Mac OS X]] very kindly creates a file called '''/var/vm/sleepimage''' on any laptop that is suspended. This file is NOT erased when the machine starts up. It is unencrypted even if the user turns on [[File Vault]] and enables Secure Virtual Memory. [http://pc-eye.blogspot.com/2008/08/live-memory-dump-on-mac-laptops.html].
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; Firewire
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: It is possible for [[Firewire]] or IEEE1394 devices to directly access the memory of a computer. Using this capability has been suggested as a method for acquiring memory images for forensic analysis. Unfortunately, the method is not safe enough to be widely used yet. There are some published papers and tools, listed below, but they are not yet forensically sound. These tools do not work with all Firewire controllers and on other can cause system crashes. The technology holds promise for future development, in general should be avoided for now.
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: At [[CanSec West 05]], [[Michael Becher]], [[Maximillian Dornseif]], and [[Christian N. Klein]] discussed an [[exploit]] which uses [[DMA]] to read arbitrary memory locations of a [[firewire]]-enabled system. The [http://md.hudora.de/presentations/firewire/2005-firewire-cansecwest.pdf paper] lists more details. The exploit is run on an [http://ipodlinux.org/Main_Page iPod running Linux]. This can be used to grab screen contents.
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: This technique has been turned into a tool that you can download from:  http://www.storm.net.nz/projects/16
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: Goldfish is a tool that is being developed to get RAM from a Mac. Contact cybercrime.com.
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== Memory Imaging Tools ==
 
===[[Windows]] Hardware===
 
; Tribble PCI Card (research project)
 
: http://www.digital-evidence.org/papers/tribble-preprint.pdf
 
  
; CoPilot by Komoku
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== Why use TDMA?==
: Komoku was acquired by Microsoft and the card was not made publicly available.
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It increases the efficiency of transmission and offers a number of other advantages.  A major pro is it can be easily adapted to transmission of data as well as voice communication.  It offers the ability to carry date rates of 64 kbps to 120 mbps, which enables options of communication such as fax, voiceband data, sms, as well as bandwidth intensive apps.  TDMA allows the user to have extended battery life since the mobile is only transmitting a portion of the time during conversations.  Furthermore, it is the most cost effective technology for upgrading a current analog system to digital.
  
; Forensic RAM Extraction Device by BBN
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==How it works==
: Not publicly available. http://www.ir.bbn.com/~vkawadia/
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===[[Windows]] Software===
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It’s necessary for TDMA to rely upon that fact that the audio signal has been digitized. These signals are divided into a number of milliseconds. TDMA is also the access technique used in the European digital standard, GSM, and the Japanese digital standard, personal digital cellular (PDC). The reason for choosing TDMA for all these standards was that it enables some vital features for system operation in an advanced cellular or PCS environment. Today, TDMA is an available, well-proven technique in commercial operation in many systems.
; winen.exe (Guidance Software - included with Encase 6.11 and higher)
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A single channel can carry all four conversations if each conversation is divided into relatively short fragments, is assigned a time slot, and is transmitted in synchronized timed.
: included on [http://www.e-fense.com/helix/ Helix 2.0]
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: http://forensiczone.blogspot.com/2008/06/winenexe-ram-imaging-tool-included-in.html
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; Win32dd
 
: included on [http://www.e-fense.com/helix/ Helix 2.0]
 
: http://win32dd.msuiche.net/
 
: http://www.msuiche.net/2008/06/14/capture-memory-under-win2k3-or-vista-with-win32dd/
 
  
; [[Mdd]] (Memory DD) ([[ManTech]])
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==Pros & Downfaults==
: included on [http://www.e-fense.com/helix/ Helix 2.0]
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: http://sourceforge.net/projects/mdd
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; F-Response with FTK imager, dd, Encase, WinHex, etc
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TDMA can be wasteful of bandwidth because time slots are allocated to specific conversations whether or not anyone was speaking at the given moment.  There is an enhanced version however, EDTMA, which attempts to correct this problem.  Unlike TDMA which waits to determine whether a subscriber is transmitting, ETDMA assigns subscribers using a dynamic method.  The data is sent through pauses which normal speech contains.  If the subscriber has something they would like to transmit, it is placed as one bit in the buffer queue. The system then scans the buffer and notices the user has something to transmit, allocating the bandwidth accordingly. However, if there is nothing to transmit, it goes to the next subscriber. This technique can be 10 times more efficient as analog transmission of TDMA.
: Beta 2.03 provides remote access to memory that can be acquired using practically any standard imaging tool
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: http://www.f-response.com/index.php?option=com_content&task=view&id=79&Itemid=2
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; MANDIANT Memoryze
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==Cell Phone Providers==
: Can capture and analyze memory. Supports reading dumps (raw/dd format) from other tools.
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: http://www.mandiant.com/software/memoryze.htm
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; [[Kntdd]]
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There are several cell phone companies competing to sell their phones and advertise their network coverage area.  They will primarily be competing within two categories: TDMA and CDMA.  The pros and cons of TDMA have been mentioned, and the companies that offer TDMA are the following:  AT&T, Cingular, Nextel, T-Mobile.  The companies that support CDMA are: ALLTEL, Amp'd Mobile, Cricket Wireless, ESPN, Quest, Sprint, Verizon, Virgin Mobile. As we can see, more companies are supporting CDMA. The question that arises is, what makes the two so different? 
: http://www.gmgsystemsinc.com/knttools/
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; [[dd]]
 
: On [[Microsoft Windows]] systems, [[dd]] can be used by an Administrator user to image memory using the ''\Device\Physicalmemory'' object. Userland access to this object is denied starting in Windows 2003 Service Pack 1 and Windows Vista.
 
  
; Windows Memory Forensic Toolkit (WMFT)
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==TDMA Vs. CDMA==
: http://forensic.seccure.net/
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: http://www.blackhat.com/presentations/bh-usa-06/BH-US-06-Burdach.pdf
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; Nigilant32
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TDMA is better for international plans and debately has better battery life. CDMA claims it has better battery life and coverage, however, Cingular is supposed to have the best coverage area and that is TDMA. All of this started however ever since CDMA was introduced in 1989, and the wireless world has been in debate over merits of TDMA and CDMA. Those who are for CDMA have claimed that its technology has bandwidth efficiency of up to 13 times that of TDMA and between 20 to 40 times that of analog transmission.  Furthermore, CDMA lovers say its spread spectrum technology is more secure and offers higher transmissin quality than TDMA because of TDMA's increased resistance to multipath distortion.   
: http://www.agilerm.net/publications_4.html
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;[[HBGary]]: Fastdump and Fastdump Pro
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Those who favor TDMA point out that there has been no successful major trial of CDMA technology that supports the capacities it claims. Not to mention, theoretical improvements in bandwidth efficiency claimed CDMA is now being approached by enhancements to TDMA technology. TDMA's evolution allows capacity increases of 20 to 40 fold over analog in the near future.  CDMA is a very expensive technology that needs $300,000 per base station, compared to $80,000 for TDMA.  Lastly, TDMA is the proven leader as the most economical digital migration path for existing AMPS networks.  No one has the final word in this debate, however, it is evident that TDMA will remain the dominant technology in the wireless market.
:http://www.hbgary.com
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:[[Fastdump]] (free with registration) Can acquire physical memory on Windows 2000 through Windows XP 32 bit but not Windows 2003 or Vista. A version of the program able to work on Windows Server 2003 and above called [[Fastdump Pro]] is rumored but is not currently available.
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===Unix===
 
;[[dd]]
 
: On Unix systems, the program [[dd]] can be used to capture the contents of [[physical memory]] using a device file (e.g. <tt>/dev/mem</tt> and <tt>/dev/kmem</tt>).  In recent Linux kernels, /dev/kmem is no longer available.  In even more recent kernels, /dev/mem has additional restrictions.  And in the most recent, /dev/mem is no longer available by default, either.  The throughout the 2.6 kernel series has been to reduce direct access to memory via pseudo-device files.  See, for example, the message accompanying this patch: http://lwn.net/Articles/267427/.
 
;[http://www.pikewerks.com/sl/ Second Look]
 
: This memory analysis product has the ability to acquire memory from Linux systems, either locally or from a remote target via DMA.
 
; Idetect (Linux)
 
: http://forensic.seccure.net/
 
  
==See Also==
 
* [[Windows Memory Analysis]]
 
* http://blogs.23.nu/RedTeam/0000/00/antville-5201/
 
* http://www.storm.net.nz/projects/16
 
* http://www.friendsglobal.com/papers/FireWire%20Memory%20Dump%20of%20Windows%20XP.pdf
 
  
 
== External Links ==
 
== External Links ==
* [http://www.syngress.com/book_catalog/sample_159749156X.PDF  Windows Memory Analysis (Sample Chapter)]
 
  
[[Category:Tools]]
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[http://en.wikipedia.org/wiki/Time_division_multiple_access TDMA]
 +
[http://www.iec.org/online/tutorials/tdma/topic04.html]
 +
[http://www.cellphoneinfo.com/index.html]

Revision as of 17:03, 3 November 2006

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TDMA - Time Division Multiple Access

TDMA (Time Division Multiple Access), has the largest network in the US.

TDMA is a digital wireless communication method allowing many users to access a single radio frequency without interference. Every individual user is given a unique time slot within each channel.


Contents

Why use TDMA?

It increases the efficiency of transmission and offers a number of other advantages. A major pro is it can be easily adapted to transmission of data as well as voice communication. It offers the ability to carry date rates of 64 kbps to 120 mbps, which enables options of communication such as fax, voiceband data, sms, as well as bandwidth intensive apps. TDMA allows the user to have extended battery life since the mobile is only transmitting a portion of the time during conversations. Furthermore, it is the most cost effective technology for upgrading a current analog system to digital.

How it works

It’s necessary for TDMA to rely upon that fact that the audio signal has been digitized. These signals are divided into a number of milliseconds. TDMA is also the access technique used in the European digital standard, GSM, and the Japanese digital standard, personal digital cellular (PDC). The reason for choosing TDMA for all these standards was that it enables some vital features for system operation in an advanced cellular or PCS environment. Today, TDMA is an available, well-proven technique in commercial operation in many systems. A single channel can carry all four conversations if each conversation is divided into relatively short fragments, is assigned a time slot, and is transmitted in synchronized timed.


Pros & Downfaults

TDMA can be wasteful of bandwidth because time slots are allocated to specific conversations whether or not anyone was speaking at the given moment. There is an enhanced version however, EDTMA, which attempts to correct this problem. Unlike TDMA which waits to determine whether a subscriber is transmitting, ETDMA assigns subscribers using a dynamic method. The data is sent through pauses which normal speech contains. If the subscriber has something they would like to transmit, it is placed as one bit in the buffer queue. The system then scans the buffer and notices the user has something to transmit, allocating the bandwidth accordingly. However, if there is nothing to transmit, it goes to the next subscriber. This technique can be 10 times more efficient as analog transmission of TDMA.

Cell Phone Providers

There are several cell phone companies competing to sell their phones and advertise their network coverage area. They will primarily be competing within two categories: TDMA and CDMA. The pros and cons of TDMA have been mentioned, and the companies that offer TDMA are the following: AT&T, Cingular, Nextel, T-Mobile. The companies that support CDMA are: ALLTEL, Amp'd Mobile, Cricket Wireless, ESPN, Quest, Sprint, Verizon, Virgin Mobile. As we can see, more companies are supporting CDMA. The question that arises is, what makes the two so different?


TDMA Vs. CDMA

TDMA is better for international plans and debately has better battery life. CDMA claims it has better battery life and coverage, however, Cingular is supposed to have the best coverage area and that is TDMA. All of this started however ever since CDMA was introduced in 1989, and the wireless world has been in debate over merits of TDMA and CDMA. Those who are for CDMA have claimed that its technology has bandwidth efficiency of up to 13 times that of TDMA and between 20 to 40 times that of analog transmission. Furthermore, CDMA lovers say its spread spectrum technology is more secure and offers higher transmissin quality than TDMA because of TDMA's increased resistance to multipath distortion.

Those who favor TDMA point out that there has been no successful major trial of CDMA technology that supports the capacities it claims. Not to mention, theoretical improvements in bandwidth efficiency claimed CDMA is now being approached by enhancements to TDMA technology. TDMA's evolution allows capacity increases of 20 to 40 fold over analog in the near future. CDMA is a very expensive technology that needs $300,000 per base station, compared to $80,000 for TDMA. Lastly, TDMA is the proven leader as the most economical digital migration path for existing AMPS networks. No one has the final word in this debate, however, it is evident that TDMA will remain the dominant technology in the wireless market.


External Links

TDMA [1] [2]