Difference between revisions of "Internet Explorer History File Format"

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(Record Formats)
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Also of interest in the file header is the location of the cache directories.  In the URL records the cache directories are given as a number, with one representing the first cache directory, two representing the second and so on.  The names of the cache directories are kept at byte offset 64 in the file.  Each directory entry is 12 bytes long of which the first eight bytes contain the directory name.
 
Also of interest in the file header is the location of the cache directories.  In the URL records the cache directories are given as a number, with one representing the first cache directory, two representing the second and so on.  The names of the cache directories are kept at byte offset 64 in the file.  Each directory entry is 12 bytes long of which the first eight bytes contain the directory name.
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 +
== Allocation bitmap ==
 +
The IE History File contains an allocation bitmap starting from offset 0x250 to 0x4000.
  
 
== Record Formats ==
 
== Record Formats ==
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Every record has a similar header that consists of 8 bytes.
 
Every record has a similar header that consists of 8 bytes.
  
typedef struct _RECORD_HEADER {
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<pre>typedef struct _RECORD_HEADER {
 
   /* 000 */ char        Signature[4];
 
   /* 000 */ char        Signature[4];
 
   /* 004 */ uint32_t    AmountOfBlocksInRecord;
 
   /* 004 */ uint32_t    AmountOfBlocksInRecord;
 
} RECORD_HEADER;</pre>
 
} RECORD_HEADER;</pre>
  
The size of the record can be determined from the amount of blocks in the record; per default the block size is 128 bytes.
+
The size of the record can be determined from the amount of blocks in the record; per default the block size is 128 bytes. Therefore, a length of <pre>05 00 00 00</pre> would indicate five blocks (because the number is stored in little-endian format) of 128 bytes for a total record length of 640 bytes.
The record can contain slack data.
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 +
The blocks that make up a record can have slack space.
  
 
Currently 4 types of records are known:
 
Currently 4 types of records are known:
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<pre>typedef struct _URL_RECORD_HEADER {
 
<pre>typedef struct _URL_RECORD_HEADER {
 
   /* 000 */ char        Signature[4];
 
   /* 000 */ char        Signature[4];
   /* 004 */ uint32_t    Length;
+
   /* 004 */ uint32_t    AmountOfBlocksInRecord;
 
   /* 008 */ FILETIME    LastModified;
 
   /* 008 */ FILETIME    LastModified;
 
   /* 010 */ FILETIME    LastAccessed;
 
   /* 010 */ FILETIME    LastAccessed;
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   /* 002 */ uint16_t    time;
 
   /* 002 */ uint16_t    time;
 
} FATTIME;</pre>
 
} FATTIME;</pre>
 
The Length field is represented by four bytes that give the number of 128 byte blocks that make up the URL record.  Therefore, a length of <pre>05 00 00 00</pre> would indicate five blocks (because the number is stored in little-endian format) of 128 bytes for a total record length of 640 bytes.
 
  
 
The actual interpretation of the "LastModified" and "LastAccessed" fields depends on the type of history file in which the record is contained. As a matter of fact, Internet Explorer uses three different types of history files, namely Daily History, Weekly History, and Main History. Other "index.dat" files are used to store cached copies of visited pages and cookies.
 
The actual interpretation of the "LastModified" and "LastAccessed" fields depends on the type of history file in which the record is contained. As a matter of fact, Internet Explorer uses three different types of history files, namely Daily History, Weekly History, and Main History. Other "index.dat" files are used to store cached copies of visited pages and cookies.

Revision as of 03:21, 6 June 2009

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Further information might be found on the discussion page.

Internet Explorer stores the web browsing history in a file called index.dat. The file contains multiple records.

File Locations

Internet Explorer history files keep a record of URLs that the browser has visited, cookies that were created by these sites, and any temporary internet files that were downloaded by the site visit. As a result, Internet Explorer history files are kept in several locations. Regardless of the information stored in the file, the file is named index.dat.

On Windows 95/98 these files were located in the following locations: %systemdir%\Temporary Internet Files\Content.ie5 %systemdir%\Cookies %systemdir%\History\History.ie5

On Windows 2000/XP the file locations have changed: %systemdir%\Documents and Settings\%username%\Local Settings\Temporary Internet Files\Content.ie5 %systemdir%\Documents and Settings\%username%\Cookies %systemdir%\Documents and Settings\%username%\Local Settings\History\history.ie5

Internet Explorer also keeps daily, weekly, and monthly history logs that will be located in subfolders of %systemdir%\Documents and Settings\%username%\Local Settings\History\history.ie5. The folders will be named MSHist<two-digit number><starting four-digit year><starting two-digit month><starting two-digit day><ending four-digit year><ending two-digit month><ending two-digit day>. For example, the folder containing data from March 26, 2008 to March 27, 2008 might be named MSHist012008032620080327.

File Header

Every version of Internet Explorer since Internet Explorer 5 has used the same structure for the file header and the individual records. Internet Explorer history files begin with:

43 6c 69 65 6e 74 20 55 72 6c 43 61 63 68 65 20 4d 4d 46 20 56 65 72 20 35 2e 32

Which represents the ascii string "Client UrlCache MMF Ver 5.2"

The next field in the file header starts at byte offset 28 and is a four byte representation of the file size. The number will be stored in little-endian format so the numbers must actually be reversed to calculate the value.

Also of interest in the file header is the location of the cache directories. In the URL records the cache directories are given as a number, with one representing the first cache directory, two representing the second and so on. The names of the cache directories are kept at byte offset 64 in the file. Each directory entry is 12 bytes long of which the first eight bytes contain the directory name.

Allocation bitmap

The IE History File contains an allocation bitmap starting from offset 0x250 to 0x4000.

Record Formats

Every record has a similar header that consists of 8 bytes.

typedef struct _RECORD_HEADER {
  /* 000 */ char        Signature[4];
  /* 004 */ uint32_t    AmountOfBlocksInRecord;
} RECORD_HEADER;
The size of the record can be determined from the amount of blocks in the record; per default the block size is 128 bytes. Therefore, a length of
05 00 00 00
would indicate five blocks (because the number is stored in little-endian format) of 128 bytes for a total record length of 640 bytes.

The blocks that make up a record can have slack space.

Currently 4 types of records are known:

  • URL
  • REDR
  • HASH
  • LEAK

URL Records

These records indicate URIs that were actually requested. They contain the location and additional data like the web server's HTTP response. They begin with the header, in hexadecimal:

55 52 4C 20

This corresponds to the string URL followed by a space.

The definition for the structure in C99 format:

typedef struct _URL_RECORD_HEADER {
  /* 000 */ char        Signature[4];
  /* 004 */ uint32_t    AmountOfBlocksInRecord;
  /* 008 */ FILETIME    LastModified;
  /* 010 */ FILETIME    LastAccessed;
  /* 018 */ FATTIME     Expires;
  /* 01c */ 
  // Not finished yet
} URL_RECORD_HEADER;
typedef struct _FILETIME {
  /* 000 */ uint32_t    lower;
  /* 004 */ uint32_t    upper;
} FILETIME;
typedef struct _FATTIME {
  /* 000 */ uint16_t    date;
  /* 002 */ uint16_t    time;
} FATTIME;

The actual interpretation of the "LastModified" and "LastAccessed" fields depends on the type of history file in which the record is contained. As a matter of fact, Internet Explorer uses three different types of history files, namely Daily History, Weekly History, and Main History. Other "index.dat" files are used to store cached copies of visited pages and cookies. The information concerning how to intepret the dates of these different files can be found on Capt. Steve Bunting's web page at the University of Delaware Computer Forensics Lab (http://128.175.24.251/forensics/default.htm). Please be aware that most free and/or open source index.dat parsing programs, as well as quite a few commercial forensic tools, are not able to correctly interpret the above dates. More specifically, they interpret all the time and dates as if the records were contained into a Daily History file regardless of the actual type of the file they are stored in.

REDR Records

REDR records are very simple records. They simply indicate that the browser was redirected to another site. REDR records always start with the string REDR (0x52 45 44 52). The next four bytes are the size of the record in little endian format. The size will indicate the number 128 byte blocks.

At offset 8 from the start of the REDR record is an unknown data field. It has been confirmed that this is not a date field.

16 bytes into the REDR record is the URL that was visited in a null-terminated string. After the URL, the REDR record appears to be padded with zeros until the end of the 128 byte block.

HASH Records

LEAK Records

External Links