Difference between pages "Malware" and "Prefetch"

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'''Malware''' is a short version of '''Malicious Software'''.
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{{Expand}}
 +
Windows Prefetch files, introduced in [[Windows|Windows XP]], are designed to speed up the application startup process. Prefetch files contain the name of the executable, a Unicode list of DLLs used by that executable, a count of how many times the executable has been run, and a timestamp indicating the last time the program was run. Although Prefetch is present in Windows 2003, by default it is only enabled for boot prefetching. The feature is also found in [[Windows|Windows Vista]], where it has been augmented with [[SuperFetch]], [[ReadyBoot]], and [[ReadyBoost]]. For SSD drives Prefetch is disabled by default [http://blogs.msdn.com/b/e7/archive/2009/05/05/support-and-q-a-for-solid-state-drives-and.aspx].
  
Malware is software used for data theft, device damage, harassment, etc. It is very similar to computer malware. It installs things such as trojans, worms, and botnets to the affected device. It is illegal to knowingly distribute malware.
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The Prefetch files are stored in the directory:
 +
<pre>
 +
%SystemRoot%\Prefetch
 +
</pre>
  
== Virus ==
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The following files can be found in the Prefetch directory:
A computer program that can automatically copy itself and infect a computer.
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* <tt>*.pf</tt>, Prefetch files;
 +
* <tt>Ag*.db</tt>, [[SuperFetch]] files;
 +
* <tt>Layout.ini</tt>;
 +
* <tt>PfPre_*.db</tt>;
 +
* <tt>PfSvPerfStats.bin</tt>
  
== Worm ==
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A Prefetch file contains the name of the application, a dash, and then an eight character hash of the location from which that application was run, and a <tt>.pf</tt> extension. The filenames should be all uppercase except for the extension. The format of hashes is not known. A sample filename for [[md5deep]] would look like: <tt>MD5DEEP.EXE-4F89AB0C.pf</tt>. If an application is run from two different locations on the drive (i.e. the user runs <tt>C:\md5deep.exe</tt> and then <tt>C:\Apps\Hashing\md5deep.exe</tt>), there will be two different prefetch files in the Prefetch folder. According to MSDN up to 128 Prefetch files can be stored in the Prefetch directory [http://blogs.msdn.com/ryanmy/archive/2005/05/25/421882.aspx].
A self-replicating computer program that can automatically infect computers on a network.
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== Trojan horse ==
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== File format ==
A computer program which appears to perform a certain action, but actually performs many different forms of codes.
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Each Prefetch file has a 4-byte signature (at offset 4) "SCCA" (or in hexadecimal notation 0x53 0x43 0x43 0x41). The signature is assumed to be preceded by a 4-byte format version indicator:
 +
* 17 (0x00000011) for [[Windows XP]] and [[Windows 2003]]
 +
* 23 (0x00000017) for [[Windows Vista]], [[Windows 2008]], [[Windows 7]] and [[Windows 2012]] (note Windows 2012 has not been confirmed)
 +
* 26 (0x0000001a) for [[Windows 8|Windows 8.1]] (note this could be Windows 8 as well but has not been confirmed)
  
== Spyware ==
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For more information about the file format see: [[Windows Prefetch File Format]]
A computer program that can automatically intercept or take partial control over the user's interaction.
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== Exploit Kit ==
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== Metadata ==
A toolkit that automates the exploitation of client-side vulnerabilities, targeting browsers and programs that a website can invoke through the browser [http://blog.zeltser.com/post/1410922437/what-are-exploit-kits]. Often utilizing a drive-by-download.
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The Prefetch file contains various metadata.
 +
* The executable's name, up to 29 characters.
 +
* The run count, or number of times the application has been run.
 +
* Volume related information, like volume path and volume serial number.
 +
* The size of the Prefetch file (sometimes referred to as end of file (EOF)).
 +
* The files and directories that were used doing the application's start-up.
  
=== Drive-by-download ===
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=== Timestamps ===
Any download that happens without a person's knowledge [http://en.wikipedia.org/wiki/Drive-by_download].
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The Prefetch file contains 2 types of timestamps
 +
* The time when the application was last ran (executed). Version 26 of the Prefetch format maintains 7 previous last run times.
 +
* The volume creation time (part of the volume information) of the volume the Prefetch file was created on.
  
== Rootkit ==
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The file system creation time of the Prefetch file indicates the first time the application was executed. Both the file system modification time of the Prefetch file and the embedded last run time indicate the last time the application was executed.
A rootkit is a stealthy type of software, typically malicious, designed to hide the existence of certain processes or programs from normal methods of detection and enable continued privileged access to an operating system.
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 +
== Prefetch hash ==
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There are multiple known hashing functions to be used for prefetch file filename hashing, namely:
 +
* SCCA XP hash function; used on Windows XP and Windows 2003
 +
* SCCA Vista hash function; used on Windows Vista
 +
* SCCA 2008 hash function; used on Windows 2008, Windows 7, (possibly: Windows 2012) and Windows 8 (including 8.1)
 +
 
 +
=== SCCA XP hash function ===
 +
A Python implementation of the SCCA XP hash function:
 +
 
 +
<pre>
 +
def ssca_xp_hash_function(filename):
 +
    hash_value = 0
 +
    for character in filename:
 +
        hash_value = ((hash_value * 37) + ord(character)) % 0x100000000
 +
        hash_value = (hash_value * 314159269) % 0x100000000
 +
        if hash_value > 0x80000000:
 +
            hash_value = 0x100000000 - hash_value
 +
 
 +
    return (abs(hash_value) % 1000000007) % 0x100000000
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</pre>
 +
 
 +
=== SCCA Vista hash function ===
 +
A Python implementation of the SCCA Vista hash function:
 +
 
 +
<pre>
 +
def ssca_vista_hash_function(filename):
 +
    hash_value = 314159
 +
    for character in filename:
 +
        hash_value = ((hash_value * 37) + ord(character)) % 0x100000000
 +
    return hash_value
 +
</pre>
 +
 
 +
=== SCCA 2008 hash function ===
 +
A Python implementation of the SCCA 2008 hash function:
 +
 
 +
<pre>
 +
def ssca_2008_hash_function(filename):
 +
    hash_value = 314159
 +
    filename_index = 0
 +
    filename_length = len(filename)
 +
    while filename_index + 8 < filename_length:
 +
        character_value = ord(filename[filename_index + 1]) * 37
 +
        character_value += ord(filename[filename_index + 2])
 +
        character_value *= 37
 +
        character_value += ord(filename[filename_index + 3])
 +
        character_value *= 37
 +
        character_value += ord(filename[filename_index + 4])
 +
        character_value *= 37
 +
        character_value += ord(filename[filename_index + 5])
 +
        character_value *= 37
 +
        character_value += ord(filename[filename_index + 6])
 +
        character_value *= 37
 +
        character_value += ord(filename[filename_index]) * 442596621
 +
        character_value += ord(filename[filename_index + 7])
 +
        hash_value = ((character_value - (hash_value * 803794207)) % 0x100000000)
 +
        filename_index += 8
 +
 
 +
    while filename_index < filename_length:
 +
      hash_value = (((37 * hash_value) + ord(filename[filename_index])) % 0x100000000)
 +
      filename_index += 1
 +
 
 +
    return hash_value
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</pre>
 +
 
 +
== Registry Keys ==
 +
<pre>
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Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters
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</pre>
 +
 
 +
The EnablePrefetcher Registry value can be used to disable prefetch.
  
 
== See Also ==
 
== See Also ==
* [[Malware analysis]]
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* [[Windows Prefetch File Format]]
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* [[SuperFetch]]
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* [[Prefetch XML]]
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* [[Windows]]
  
 
== External Links ==
 
== External Links ==
* [http://en.wikipedia.org/wiki/Malware Wikipedia: malware]
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* [http://msdn.microsoft.com/msdnmag/issues/01/12/XPKernel/default.aspx More detail from Microsoft]
* [http://en.wikipedia.org/wiki/Drive-by_download Wikipedia: drive-by-download]
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* [http://en.wikipedia.org/wiki/Prefetcher Wikipedia Prefetcher]
* [http://www.viruslist.com/ Viruslist.com]
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* [http://msdn.microsoft.com/en-us/library/ms940847(v=winembedded.5).aspx MSDN: Disabling Prefetch]
* [http://code.google.com/p/androguard/wiki/DatabaseAndroidMalwares Androguard]: A list of recognized Android malware
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* [http://www.microsoft.com/whdc/driver/kernel/XP_kernel.mspx Kernel Enhancements for Windows XP], by [[Microsoft]], January 13, 2003 (Microsoft's description of Prefetch when Windows XP was introduced)
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* [http://blogs.msdn.com/b/ryanmy/archive/2005/05/25/421882.aspx Misinformation and the The Prefetch Flag], MSDN Blogs, May 25, 2005
 +
* [http://windowsir.blogspot.ch/2005/07/prefetch-file-metadata.html Prefetch file metadata], by [[Harlan Carvey]], July 13, 2005
 +
* [http://windowsir.blogspot.ch/2006/04/prefetch-files-revisited.html Prefetch files, revisited], by [[Harlan Carvey]], April 13, 2006
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* [http://blogs.msdn.com/b/e7/archive/2009/05/05/support-and-q-a-for-solid-state-drives-and.aspx Support and Q&A for Solid-State Drives], by Steven Sinofsky, May 5, 2009
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* [http://computer-forensics.sans.org/blog/2009/08/05/de-mystifying-defrag-identifying-when-defrag-has-been-used-for-anti-forensics-part-1-windows-xp/ De-mystifying Defrag: Identifying When Defrag Has Been Used for Anti-Forensics (Part 1 - Windows XP)], by [[Chad Tilbury]], August 5, 2009
 +
* [http://www.swiftforensics.com/2010/04/the-windows-prefetchfile.html Windows Prefetch File (old blog entry from 42 LLC)], by [[Yogesh Khatri]], April 14, 2010
 +
* [http://www.dfinews.com/articles/2010/12/decoding-prefetch-files-forensic-purposes-part-1 Decoding Prefetch Files for Forensic Purposes: Part 1], by [[Mark Wade]], December 8, 2010
 +
* [http://crucialsecurityblog.harris.com/2011/04/11/prefetch-files-at-face-value/ Prefetch Files at Face Value], by [[Mark Wade]], April 11, 2011
 +
* [http://kitrap08.blogspot.hk/2011/07/windows-logical-prefetcher.html Windows Logical Prefetcher], TTS blog, July 30, 2011 (article is in Russian)
 +
* [http://labit.in/pliki-prefetch-w-windows/ Prefetch i niedokładny licznik] by Paweł Hałdrzyński, August 20, 2011 (article in Polish; uncertain about the year of publication)
 +
* [http://windowsir.blogspot.ch/2012/03/prefetch-analysis-revisited.html Prefetch Analysis, Revisited], by [[Harlan Carvey]], March 8, 2012
 +
* [http://windowsir.blogspot.ch/2012/03/prefetch-analysis-revisitedagain.html Prefetch Analysis, Revisited...Again...], by [[Harlan Carvey]], March 15, 2012
 +
* [http://www.hexacorn.com/blog/2012/06/13/prefetch-hash-calculator-a-hash-lookup-table-xpvistaw7w2k3w2k8/ Prefetch Hash Calculator + a hash lookup table xp/vista/w7/w2k3/w2k8], Hexacorn blog, June 13, 2012
 +
* [http://www.hexacorn.com/blog/2012/10/29/prefetch-file-names-and-unc-paths/ Prefetch file names and UNC paths], Hexacorn blog, October 29, 2012
 +
* [http://journeyintoir.blogspot.ch/2012/12/ntosboot-prefetch-file.html NTOSBOOT Prefetch File], by [[Corey Harrell]], December 5, 2012
 +
* [http://www.invoke-ir.com/2013/09/whats-new-in-prefetch-for-windows-8.html What's New in the Prefetch for Windows 8??], by Jared Atkinson, September 21, 2013
 +
* [http://www.swiftforensics.com/2013/10/windows-prefetch-pf-files.html?m=1 Windows Prefetch (.PF) files], by [[Yogesh Khatri]], October 21, 2013
 +
* [http://resources.infosecinstitute.com/windows-systems-artifacts-digital-forensics-part-iii-prefetch-files/ Windows Systems and Artifacts in Digital Forensics: Part III: Prefetch Files], by Ivan Dimov, November 21, 2013
 +
* [http://i.imgur.com/riuljsK.jpg Prefetch 101 -  a Windows 8 Prefetch file walkthrough], by Jared Atkinson, 2014
 +
 
 +
== Tools ==
  
=== Analysis ===
+
=== Commercial ===
* [http://sempersecurus.blogspot.ch/2013/12/a-forensic-overview-of-linux-perlbot.html A Forensic Overview of a Linux perlbot], by Andre M. DiMino, December 17, 2013
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* [http://research.zscaler.com/2014/02/probing-into-flash-zero-day-exploit-cve.html Probing into the Flash Zero Day Exploit (CVE-2014-0502)], by Krishnan Subramanian, February 21, 2014
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* [http://www.welivesecurity.com/wp-content/uploads/2014/03/operation_windigo.pdf Operation Windigo], by Olivier Bilodeau, Pierre-Marc Bureau, Joan Calvet, Alexis Dorais-Joncas, Marc-Étienne M.Léveillé, Benjamin Vanheuverzwijn, March, 2014
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* [http://blogs.technet.com/b/srd/archive/2014/03/24/security-advisory-2953095-recommendation-to-stay-protected-and-for-detections.aspx Security Advisory 2953095: recommendation to stay protected and for detections\, by Chengyun Chu, Elia Florio, March 24, 2014
+
  
=== Exploit Kit ===
+
=== Free - Non Open Source ===
* [http://blog.zeltser.com/post/1410922437/what-are-exploit-kits What Are Exploit Kits?], by [[Lenny Zeltser]], October 26, 2010
+
* [http://www.woanware.co.uk/forensics/prefetchforensics.html PrefetchForensics], PrefetchForensics is an application to extract information from Windows Prefetch files
* [http://nakedsecurity.sophos.com/2013/07/02/the-four-seasons-of-glazunov-digging-further-into-sibhost-and-flimkit/ The four seasons of Glazunov: digging further into Sibhost and Flimkit], by Fraser Howard, July 2, 2013
+
* [http://redwolfcomputerforensics.com/index.php?option=com_content&task=view&id=42&Itemid=55 Prefetch-Parser], Parse the prefetch files and display information
* [http://www.kahusecurity.com/2013/kore-exploit-kit/ Kore Exploit Kit], Kahu Security blog, July 18, 2013
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* [http://www.mitec.cz/wfa.html Windows File Analyzer] - Parses Prefetch files, thumbnail databases, shortcuts, index.dat files, and the recycle bin
 +
* [http://www.tzworks.net/prototype_page.php?proto_id=1 Windows Prefetch Parser (pf)], Free tool that can be run on Windows, Linux or Mac OS-X
  
=== Rootkit ===
+
=== Open Source ===
* [http://en.wikipedia.org/wiki/Rootkit Wikipedia: Rootkit]
+
* [https://code.google.com/p/prefetch-tool/ prefetch-tool], Script to extract information from windows prefetch folder
* [http://articles.forensicfocus.com/2013/11/22/understanding-rootkits/ Understanding Rootkits: Using Memory Dump Analysis for Rootkit Detection], by Dmitry Korolev, Yuri Gubanov, Oleg Afonin, November 22, 2013
+
* [http://bitbucket.cassidiancybersecurity.com/prefetch-parser prefetch-parser], Standalone Python tools that parses Windows prefetch files and extracts all known and forensically relevant artefacts contained.
  
[[Category:Malware]]
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[[Category:Windows]]

Revision as of 00:02, 15 April 2014

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Please help to improve this article by expanding it.
Further information might be found on the discussion page.

Windows Prefetch files, introduced in Windows XP, are designed to speed up the application startup process. Prefetch files contain the name of the executable, a Unicode list of DLLs used by that executable, a count of how many times the executable has been run, and a timestamp indicating the last time the program was run. Although Prefetch is present in Windows 2003, by default it is only enabled for boot prefetching. The feature is also found in Windows Vista, where it has been augmented with SuperFetch, ReadyBoot, and ReadyBoost. For SSD drives Prefetch is disabled by default [1].

The Prefetch files are stored in the directory:

%SystemRoot%\Prefetch

The following files can be found in the Prefetch directory:

  • *.pf, Prefetch files;
  • Ag*.db, SuperFetch files;
  • Layout.ini;
  • PfPre_*.db;
  • PfSvPerfStats.bin

A Prefetch file contains the name of the application, a dash, and then an eight character hash of the location from which that application was run, and a .pf extension. The filenames should be all uppercase except for the extension. The format of hashes is not known. A sample filename for md5deep would look like: MD5DEEP.EXE-4F89AB0C.pf. If an application is run from two different locations on the drive (i.e. the user runs C:\md5deep.exe and then C:\Apps\Hashing\md5deep.exe), there will be two different prefetch files in the Prefetch folder. According to MSDN up to 128 Prefetch files can be stored in the Prefetch directory [2].

File format

Each Prefetch file has a 4-byte signature (at offset 4) "SCCA" (or in hexadecimal notation 0x53 0x43 0x43 0x41). The signature is assumed to be preceded by a 4-byte format version indicator:

For more information about the file format see: Windows Prefetch File Format

Metadata

The Prefetch file contains various metadata.

  • The executable's name, up to 29 characters.
  • The run count, or number of times the application has been run.
  • Volume related information, like volume path and volume serial number.
  • The size of the Prefetch file (sometimes referred to as end of file (EOF)).
  • The files and directories that were used doing the application's start-up.

Timestamps

The Prefetch file contains 2 types of timestamps

  • The time when the application was last ran (executed). Version 26 of the Prefetch format maintains 7 previous last run times.
  • The volume creation time (part of the volume information) of the volume the Prefetch file was created on.

The file system creation time of the Prefetch file indicates the first time the application was executed. Both the file system modification time of the Prefetch file and the embedded last run time indicate the last time the application was executed.

Prefetch hash

There are multiple known hashing functions to be used for prefetch file filename hashing, namely:

  • SCCA XP hash function; used on Windows XP and Windows 2003
  • SCCA Vista hash function; used on Windows Vista
  • SCCA 2008 hash function; used on Windows 2008, Windows 7, (possibly: Windows 2012) and Windows 8 (including 8.1)

SCCA XP hash function

A Python implementation of the SCCA XP hash function:

def ssca_xp_hash_function(filename):
    hash_value = 0
    for character in filename:
        hash_value = ((hash_value * 37) + ord(character)) % 0x100000000
        hash_value = (hash_value * 314159269) % 0x100000000
        if hash_value > 0x80000000:
            hash_value = 0x100000000 - hash_value

    return (abs(hash_value) % 1000000007) % 0x100000000

SCCA Vista hash function

A Python implementation of the SCCA Vista hash function:

def ssca_vista_hash_function(filename):
    hash_value = 314159
    for character in filename:
        hash_value = ((hash_value * 37) + ord(character)) % 0x100000000
    return hash_value

SCCA 2008 hash function

A Python implementation of the SCCA 2008 hash function:

def ssca_2008_hash_function(filename):
    hash_value = 314159
    filename_index = 0
    filename_length = len(filename)
    while filename_index + 8 < filename_length:
        character_value = ord(filename[filename_index + 1]) * 37
        character_value += ord(filename[filename_index + 2])
        character_value *= 37
        character_value += ord(filename[filename_index + 3])
        character_value *= 37
        character_value += ord(filename[filename_index + 4])
        character_value *= 37
        character_value += ord(filename[filename_index + 5])
        character_value *= 37
        character_value += ord(filename[filename_index + 6])
        character_value *= 37
        character_value += ord(filename[filename_index]) * 442596621
        character_value += ord(filename[filename_index + 7])
        hash_value = ((character_value - (hash_value * 803794207)) % 0x100000000)
        filename_index += 8

    while filename_index < filename_length: 
       hash_value = (((37 * hash_value) + ord(filename[filename_index])) % 0x100000000)
       filename_index += 1

    return hash_value 

Registry Keys

Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters

The EnablePrefetcher Registry value can be used to disable prefetch.

See Also

External Links

Tools

Commercial

Free - Non Open Source

Open Source

  • prefetch-tool, Script to extract information from windows prefetch folder
  • prefetch-parser, Standalone Python tools that parses Windows prefetch files and extracts all known and forensically relevant artefacts contained.