Difference between pages "Google Chrome" and "Computer forensics"

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Google Chrome is a [[Web Browser|web browser]] developed by Google Inc.
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Computer forensics is the practice of identifying, extracting and considering evidence from digital media such as computer hard drives. [[Digital evidence]] is both fragile and volatile and requires the attention of a certified specialist to ensure that materials of evidentiary value can be effectively isolated and extracted in a scientific manner that will bear the scrutiny of a court of law.  
 
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Computer forensics is not to be confused with the more generic term of 'forensic computing', which refers to the analysis and study of all types of digital media and materials - whether they be of a computing or telecommunication nature. Computer forensics, in a strict sense, applies specifically to the evaluation of computers and data storage or data processing devices.
== Configuration ==
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The Google Chrome configuration can be found in the '''Preferences''' file.
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On Linux
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<pre>
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/home/$USER/.config/google-chrome/Default/Preferences
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</pre>
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On MacOS-X
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<pre>
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/Users/$USER/Library/Application Support/Google/Chrome/Default/Preferences
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</pre>
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On Windows XP
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<pre>
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C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Default\Preferences
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</pre>
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On Windows Vista and later
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Preferences
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</pre>
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Or for '''Chrome SxS''' (Chrome side-by-side)
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome SxS\User Data\Default\Preferences
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</pre>
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Or for '''Chromium'''
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On Linux
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<pre>
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/home/$USER/.config/chromium/Default/Preferences
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</pre>
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On MacOS-X
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<pre>
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/Users/$USER/Library/Application Support/Chromium/Default/Preferences
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</pre>
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On Windows XP
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<pre>
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C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Chromium\User Data\Default\Preferences
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</pre>
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On Windows Vista and later
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Chromium\User Data\Default\Preferences
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</pre>
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=== Plugins ===
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Information about plugins can be found under the "plugins section" of the Preferences file.
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=== DNS Prefetching ===
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DNS is prefetched for related sites, e.g. links on the page.
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This behavior is controlled by the setting "Predict network actions to improve page load performance", which is enabled by default.
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If enabled the Preferences file contains:
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<pre>
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  "dns_prefetching": {
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      "enabled": true,
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</pre>
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If disabled the Preferences file contains:
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<pre>
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  "dns_prefetching": {
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      "enabled": false,
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</pre>
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== Start-up DNS queries ==
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When Chrome starts it queries for several non-existing hostnames that consists of a 10 random characters, E.g.
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<pre>
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ttrgoiknff.mydomain.com
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bxjhgftsyu.mydomain.com
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yokjbjiagd.mydomain.com
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</pre>
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This is used to determine if your ISP is hijacking NXDOMAIN results [http://www.google.com/support/forum/p/Chrome/thread?tid=3511015c72a7b314&hl=en].
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== Disk Cache ==
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Google Chrome uses multiple caches, from [http://src.chromium.org/viewvc/chrome/trunk/src/net/base/cache_type.h?view=markup]:
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<pre>
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// The types of caches that can be created.
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enum CacheType {
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    DISK_CACHE,  // Disk is used as the backing storage.
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    MEMORY_CACHE,  // Data is stored only in memory.
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    MEDIA_CACHE,  // Optimized to handle media files.
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    APP_CACHE,  // Backing store for an AppCache.
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    SHADER_CACHE, // Backing store for the GL shader cache.
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    PNACL_CACHE, // Backing store the PNaCl translation cache
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};
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</pre>
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<b>Note that $PROFILE (or %PROFILE%) the paths below is the profile dependent subdirectory which is normally Default but also could be Profile1, Profile2, etc.</b>
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The Google Chrome disk cache uses the [[Chrome Disk Cache Format]] and can be found in:
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On Linux
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<pre>
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/home/$USER/.cache/chromium/$PROFILE/Cache/
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/home/$USER/.cache/google-chrome/$PROFILE/Cache/
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/home/$USER/.config/chromium/$PROFILE/Cache/
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/home/$USER/.config/google-chrome/$PROFILE/Cache/
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</pre>
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<pre>
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/home/$USER/.cache/chromium/$PROFILE/Media Cache/
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/home/$USER/.cache/google-chrome/$PROFILE/Media Cache/
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/home/$USER/.config/chromium/$PROFILE/Media Cache/
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/home/$USER/.config/google-chrome/$PROFILE/Media Cache/
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</pre>
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<pre>
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/home/$USER/.config/chromium/$PROFILE/Application Cache/Cache/
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/home/$USER/.config/google-chrome/$PROFILE/Application Cache/Cache/
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</pre>
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<pre>
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/home/$USER/.config/chromium/$PROFILE/GPUCache/
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/home/$USER/.config/google-chrome/$PROFILE/GPUCache/
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</pre>
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<pre>
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/home/$USER/.cache/chromium/PnaclTranslationCache/
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/home/$USER/.cache/google-chrome/PnaclTranslationCache/
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</pre>
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On MacOS-X
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<pre>
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/Users/$USER/Library/Caches/Chromium/$PROFILE/Cache
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/Users/$USER/Library/Caches/Google/Chrome/$PROFILE/Cache
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</pre>
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<b>TODO confirm the following paths</b>
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<pre>
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/Users/$USER/Caches/Chromium/$PROFILE/Cache/
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/Users/$USER/Caches/Google/Chrome/$PROFILE/Cache/
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</pre>
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<pre>
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/Users/$USER/Library/Caches/Chromium/$PROFILE/Media Cache
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/Users/$USER/Library/Caches/Google/Chrome/$PROFILE/Media Cache
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</pre>
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<pre>
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/Users/$USER/Library/Application Support/Chromium/$PROFILE/Application Cache/Cache/
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/Users/$USER/Library/Application Support/Google/Chrome/$PROFILE/Application Cache/Cache/
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</pre>
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<pre>
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/Users/$USER/Library/Application Support/Chromium/$PROFILE/GPUCache/
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/Users/$USER/Library/Application Support/Google/Chrome/$PROFILE/GPUCache/
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</pre>
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<pre>
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/Users/$USER/Library/Caches/Chromium/PnaclTranslationCache/
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/Users/$USER/Library/Caches/Google/Chrome/PnaclTranslationCache/
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</pre>
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On Windows XP
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<b>TODO confirm the following paths</b>
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<pre>
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C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Chromium\User Data\Cache\
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C:\Documents and Settings\%USERNAME%\Local Settings\Application Data\Google\Chrome\User Data\Cache\
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</pre>
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On Windows Vista and later
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chromium\%PROFILE%\Cache\
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\%PROFILE%\Cache\
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</pre>
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chromium\%PROFILE%\Application Cache\Cache\
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\%PROFILE%\Application Cache\Cache\
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</pre>
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chromium\%PROFILE%\Media Cache\
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\%PROFILE%\Media Cache\
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</pre>
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<pre>
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C:\Users\%USERNAME%\AppData\Local\Google\Chromium\%PROFILE%\GPUCache\
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C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\%PROFILE%\GPUCache\
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</pre>
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The Chrome Cache contains different files with the following file names:
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* index
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* data_#; where # contains a decimal digit.
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* f_######; where # contains a hexadecimal digit.
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== History ==
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Chrome stores the history of visited sites in a file named '''History'''. This file uses the [[SQLite database format]].
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The '''History''' file can be found in same location as the '''Preferences''' file.
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There is also '''Archived History''' that predates information in the '''History''' file.
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Note that the '''Archived History''' only contains visits.
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=== Timestamps ===
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The '''History''' file uses the different timestamps.
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==== visits.visit_time ====
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The '''visits.visit_time''' is in (the number of) microseconds since January 1, 1601 UTC
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Some Python code to do the conversion into human readable format:
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<pre>
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date_string = datetime.datetime( 1601, 1, 1 )
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            + datetime.timedelta( microseconds=timestamp )
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</pre>
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Note that this timestamp is not the same as a Windows filetime which is (the number of) 100 nanoseconds since January 1, 1601 UTC
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==== downloads.start_time ====
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The '''downloads.start_time''' is in (the number of) seconds since January 1, 1970 UTC
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Some Python code to do the conversion into human readable format:
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<pre>
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date_string = datetime.datetime( 1970, 1, 1 )
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            + datetime.timedelta( seconds=timestamp )
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</pre>
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=== Example queries ===
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Some example queries:
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To get an overview of the visited sites:
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<pre>
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SELECT datetime(((visits.visit_time/1000000)-11644473600), "unixepoch"), urls.url, urls.title FROM urls, visits WHERE urls.id = visits.url;
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</pre>
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Note that the visit_time conversion looses precision.
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To get an overview of the downloaded files:
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<pre>
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SELECT datetime(downloads.start_time, "unixepoch"), downloads.url, downloads.full_path, downloads.received_bytes, downloads.total_bytes FROM downloads;
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</pre>
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How the information of the downloaded files is stored in the database can vary per version of Chrome as of version 26:
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<pre>
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SELECT datetime(((downloads.start_time/1000000)-11644473600), "unixepoch"), downloads.target_path, downloads_url_chains.url, downloads.received_bytes, downloads.total_bytes \
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FROM downloads, downloads_url_chains WHERE downloads.id = downloads_url_chains.id;
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</pre>
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== Cookies ==
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Chrome stores the cookies in a file named '''Cookies'''. This file uses the [[SQLite database format]].
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=== Extension Cookies ===
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Chrome stores the cookies used by extensions in a file named '''Extension Cookies'''. This file uses the [[SQLite database format]].
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<pre>
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SELECT datetime(((cookies.creation_utc/1000000)-11644473600), "unixepoch"), cookies.host_key, cookies.name, cookies.value, cookies.path, \
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datetime(((cookies.expires_utc/1000000)-11644473600), "unixepoch"), cookies.secure, cookies.httponly, datetime(((cookies.last_access_utc/1000000)-11644473600), "unixepoch"), \
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cookies.has_expires, cookies.persistent, cookies.priority FROM cookies;
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</pre>
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== See Also ==
 
== See Also ==
* [[Chrome Disk Cache Format]]
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* [[File Analysis]]
* [[SQLite database format]]
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* [[Malware analysis]]
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* [[Memory analysis]]
  
 
== External Links ==
 
== External Links ==
* [http://en.wikipedia.org/wiki/Google_Chrome Wikipedia article on Google Chrome]
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* [http://en.wikipedia.org/wiki/Computer_forensics Wikipedia: Computer forensics]
* [http://www.chromium.org/user-experience/user-data-directory The Chromium Projects - User Data Directory]
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* [http://www.wikicrimeline.co.uk/index.php?title=Digital_evidence WikiCrimeLine Digital evidence]
* [http://www.chromium.org/developers/design-documents/network-stack/disk-cache Chrome Disk Cache]
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* [http://www.wikicrimeline.co.uk/index.php?title=Computer_forensics WikiCrimeLine Computer forensics]
* [http://www.google.com/support/forum/p/Chrome/thread?tid=3511015c72a7b314&hl=en Chrome support forum article random 10 character hostnames on startup]
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* [http://www.useragentstring.com/pages/Chrome/ Chrome User Agent strings]
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* [http://computer-forensics.sans.org/blog/2010/01/21/google-chrome-forensics/ Google Chrome Forensics] by [[Kristinn Guðjónsson]], January 21, 2010
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* [http://linuxsleuthing.blogspot.ch/2013/02/cashing-in-on-google-chrome-cache.html?m=1 Cashing in on the Google Chrome Cache], [[John Lehr]], February 24, 2013
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* [http://www.obsidianforensics.com/blog/history-index-files-removed-from-chrome/ History Index files removed from Chrome v30], by Ryan Benson, October 2, 2013
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* [https://hindsight-internet-history.googlecode.com/files/Evolution_of_Chrome_Databases.png Evolution of Chrome Databases], by Ryan Benson, November 12, 2013
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== Tools ==
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=== Open Source ===
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* [https://code.google.com/p/hindsight-internet-history/ hindsight-internet-history]
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[[Category:Applications]]
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[[Category:Web Browsers]]
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Revision as of 02:34, 25 June 2014

Computer forensics is the practice of identifying, extracting and considering evidence from digital media such as computer hard drives. Digital evidence is both fragile and volatile and requires the attention of a certified specialist to ensure that materials of evidentiary value can be effectively isolated and extracted in a scientific manner that will bear the scrutiny of a court of law. Computer forensics is not to be confused with the more generic term of 'forensic computing', which refers to the analysis and study of all types of digital media and materials - whether they be of a computing or telecommunication nature. Computer forensics, in a strict sense, applies specifically to the evaluation of computers and data storage or data processing devices.

See Also

External Links