Difference between revisions of "Windows Prefetch File Format"

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(Section D - Volume information (block))
(Section A - Metrics array)
 
(33 intermediate revisions by the same user not shown)
Line 97: Line 97:
 
The format of the file information is version dependent.
 
The format of the file information is version dependent.
  
The the file information is sometimes considered part of the file header.  
+
Note that some other format specifications consider the file information part of the file header.  
  
 
==== File information - version 17 ====
 
==== File information - version 17 ====
Line 292: Line 292:
  
 
==== File information - version 26 ====
 
==== File information - version 26 ====
The file information – version 23 is 224 bytes of size and consists of:
+
The file information – version 26 is 224 bytes of size and consists of:
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
Line 405: Line 405:
 
|}
 
|}
  
== Section A ==
+
== Section A - Metrics array ==
This section contains an array with 20 byte (version 17) or 32 byte (version 23 and 26) entry records.
+
==== Metrics entry record - version 17 ====
 +
The metrics entry records – version 17 is 20 bytes in size and consists of:
  
The actual format and usage of these entry records is currently not known.
+
{| class="wikitable"
 +
|-
 +
! Field
 +
! Offset
 +
! Length
 +
! Type
 +
! Notes
 +
|-
 +
|
 +
| 0
 +
| 4
 +
| DWORD
 +
| Start time in ms
 +
|-
 +
|
 +
| 4
 +
| 4
 +
| DWORD
 +
| Duration in ms
 +
|-
 +
|
 +
| 8
 +
| 4
 +
| DWORD
 +
| Filename string offset <br> The offset is relative to the start of the filename string section (section C)
 +
|-
 +
|
 +
| 12
 +
| 4
 +
| DWORD
 +
| Filename string number of characters without end-of-string character
 +
|-
 +
|
 +
| 16
 +
| 4
 +
| DWORD
 +
| Unknown, flags?
 +
|}
  
== Section B ==
+
==== Metrics entry record - version 23 ====
 +
The metrics entry records – version 23 is 32 bytes in size and consists of:
 +
 
 +
{| class="wikitable"
 +
|-
 +
! Field
 +
! Offset
 +
! Length
 +
! Type
 +
! Notes
 +
|-
 +
|
 +
| 0
 +
| 4
 +
| DWORD
 +
| Start time in ms
 +
|-
 +
|
 +
| 4
 +
| 4
 +
| DWORD
 +
| Duration in ms
 +
|-
 +
|
 +
| 8
 +
| 4
 +
| DWORD
 +
| Average duration in ms?
 +
|-
 +
|
 +
| 12
 +
| 4
 +
| DWORD
 +
| Filename string offset <br> The offset is relative to the start of the filename string section (section C)
 +
|-
 +
|
 +
| 16
 +
| 4
 +
| DWORD
 +
| Filename string number of characters without end-of-string character
 +
|-
 +
|
 +
| 20
 +
| 4
 +
| DWORD
 +
| Unknown, flags?
 +
|-
 +
|
 +
| 24
 +
| 8
 +
|
 +
| NTFS file reference <br> 0 if not set.
 +
|}
 +
 
 +
==== Metrics entry record - version 26 ====
 +
The metrics entry record – version 26 appears to be similar to metrics entry record – version 23.
 +
 
 +
== Section B - Trace chains array ==
 
This section contains an array with 12 byte (version 17, 23 and 26) entry records.
 
This section contains an array with 12 byte (version 17, 23 and 26) entry records.
  
The actual format and usage of these entry records is currently not known.
+
{| class="wikitable"
 +
|-
 +
! Field
 +
! Offset
 +
! Length
 +
! Type
 +
! Notes
 +
|-
 +
|
 +
| 0
 +
| 4
 +
|
 +
| Next array entry index <br> Contains the next trace chain array entry index in the chain, where the first entry index starts with 0, or -1 (0xffffffff) for the end-of-chain.
 +
|-
 +
|
 +
| 4
 +
| 4
 +
|
 +
| Total block load count <br> Number of blocks loaded (or fetched) <br> The block size 512k (512 x 1024) bytes
 +
|-
 +
|
 +
| 8
 +
| 1
 +
|
 +
| Unknown
 +
|-
 +
|
 +
| 9
 +
| 1
 +
|
 +
| Sample duration in ms?
 +
|-
 +
|
 +
| 10
 +
| 2
 +
|
 +
| Unknown
 +
|}
  
 
== Section C - Filename strings ==
 
== Section C - Filename strings ==
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At the end of the section there seems to be alignment padding that can contain remnant values.
 
At the end of the section there seems to be alignment padding that can contain remnant values.
  
== Section D - Volume information (block) ==
+
== Section D - Volumes information (block) ==
  
 
Section D contains one or more subsections, each subsection refers to directories on a volume.
 
Section D contains one or more subsections, each subsection refers to directories on a volume.
Line 588: Line 720:
 
|-
 
|-
 
|}
 
|}
 +
 +
==== Volume information - version 26 ====
 +
The volume information entry – version 26 appears to be similar to volume information – version 23.
  
 
=== Sub section E - NTFS file references ===
 
=== Sub section E - NTFS file references ===
<b>TODO</b>
+
This sub section can contain NTFS file references.
 +
 
 +
For more information see [https://googledrive.com/host/0B3fBvzttpiiSbl9XZGZzQ05hZkU/Windows%20Prefetch%20File%20(PF)%20format.pdf Windows Prefetch File (PF) format].
  
 
=== Sub section F - Directory strings ===
 
=== Sub section F - Directory strings ===
<b>TODO</b>
+
This sub sections contains directory strings. The number of strings is stored in the volume information.
 +
 
 +
A directory string is stored in the following structure:
 +
{| class="wikitable"
 +
|-
 +
! Field
 +
! Offset
 +
! Length
 +
! Type
 +
! Notes
 +
|-
 +
|
 +
| 0x0000
 +
| 2
 +
| DWORD
 +
| Number of characters (WORDs) of the directory name. The value does not include the end-of-string character.
 +
|-
 +
|
 +
| 0x0002
 +
|
 +
| USTR
 +
| The directory name as a Unicode (UTF-16 litte-endian string) terminated by an end-of-string character (U+0000).
 +
|-
 +
|}
  
 
== See Also ==
 
== See Also ==
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== External Links ==
 
== External Links ==
 
* [https://googledrive.com/host/0B3fBvzttpiiSbl9XZGZzQ05hZkU/Windows%20Prefetch%20File%20(PF)%20format.pdf Windows Prefetch File (PF) format], by the [[libssca|libssca project]]
 
* [https://googledrive.com/host/0B3fBvzttpiiSbl9XZGZzQ05hZkU/Windows%20Prefetch%20File%20(PF)%20format.pdf Windows Prefetch File (PF) format], by the [[libssca|libssca project]]
 +
* [http://bitbucket.cassidiancybersecurity.com/prefetch-parser/wiki/Home Windows Prefetch file format], by the [http://bitbucket.cassidiancybersecurity.com/prefetch-parser prefetch-parser] project.
  
 
[[Category:File Formats]]
 
[[Category:File Formats]]

Latest revision as of 04:12, 29 June 2014

Information icon.png

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

A Windows Prefetch file consists of one file header and multiple file sections with different content. Not all content has an obvious forensic value.

As far as have been possible to ascertain, there is no public description of the format. The description below has been synthesised from examination of multiple prefetch files.

Characteristics

Integers stored in little-endian
Strings Stored as UTF-16 little-endian without a byte-order-mark (BOM).
Timestamps Stored as Windows FILETIME in UTC.

File header

The file header is 84 bytes of size and consists of:

Field Offset Length Type Notes
H1 0x0000 4 DWORD Format version (see format version section below)
H2 0x0004 4 DWORD Signature 'SCCA' (or in hexadecimal representation 0x53 0x43 0x43 0x4)
H3 0x0008 4 DWORD? Unknown - Values observed: 0x0F - Windows XP, 0x11 - Windows 7, Windows 8.1
H4 0x000C 4 DWORD Prefetch file size (or length) (sometimes referred to as End of File (EOF)).
H5 0x0010 60 USTR The name of the (original) executable as a Unicode (UTF-16 litte-endian string), up to 29 characters and terminated by an end-of-string character (U+0000). This name should correspond with the one in the prefetch file filename.
H6 0x004C 4 DWORD The prefetch hash. This hash value should correspond with the one in the prefetch file filename.
H7 0x0050 4 ? Unknown (flags)? Values observed: 0 for almost all prefetch files (XP); 1 for NTOSBOOT-B00DFAAD.pf (XP)

It's worth noting that the name of a carved prefetch file can be restored using the information in field H5 and H6, and its size can be determined by field H4.

Format version

Value Windows version
17 (0x11) Windows XP, Windows 2003
23 (0x17) Windows Vista, Windows 7
26 (0x1a) Windows 8.1 (note this could be Windows 8 as well but has not been confirmed)

File information

The format of the file information is version dependent.

Note that some other format specifications consider the file information part of the file header.

File information - version 17

The file information – version 17 is 68 bytes of size and consists of:

Field Offset Length Type Notes
0x0054 4 DWORD The offset to section A. The offset is relative from the start of the file.
0x0058 4 DWORD The number of entries in section A.
0x005C 4 DWORD The offset to section B. The offset is relative from the start of the file.
0x0060 4 DWORD The number of entries in section B.
0x0064 4 DWORD The offset to section C. The offset is relative from the start of the file.
0x0068 4 DWORD Length of section C.
0x006C 4 DWORD Offset to section D. The offset is relative from the start of the file.
0x0070 4 DWORD The number of entries in section D.
0x0074 4 DWORD Length of section D.
0x0078 8 FILETIME Latest execution time (or run time) of executable (FILETIME)
0x0080 16  ? Unknown ? Possibly structured as 4 DWORD. Observed values: /0x00000000 0x00000000 0x00000000 0x00000000/, /0x47868c00 0x00000000 0x47860c00 0x00000000/ (don't exclude the possibility here that this is remnant data)
0x0090 4 DWORD Execution counter (or run count)
0x0094 4 DWORD? Unknown ? Observed values: 1, 2, 3, 4, 5, 6 (XP)

File information - version 23

The file information – version 23 is 156 bytes of size and consists of:

Field Offset Length Type Notes
0x0054 4 DWORD The offset to section A. The offset is relative from the start of the file.
0x0058 4 DWORD The number of entries in section A.
0x005C 4 DWORD The offset to section B. The offset is relative from the start of the file.
0x0060 4 DWORD The number of entries in section B.
0x0064 4 DWORD The offset to section C. The offset is relative from the start of the file.
0x0068 4 DWORD Length of section C.
0x006C 4 DWORD Offset to section D. The offset is relative from the start of the file.
0x0070 4 DWORD The number of entries in section D.
0x0074 4 DWORD Length of section D.
0x0078 8 ? Unknown
0x0080 8 FILETIME Latest execution time (or run time) of executable (FILETIME)
0x0088 16  ? Unknown
0x0098 4 DWORD Execution counter (or run count)
0x009C 4 DWORD? Unknown
0x00A0 80 ? Unknown

File information - version 26

The file information – version 26 is 224 bytes of size and consists of:

Field Offset Length Type Notes
0x0054 4 DWORD The offset to section A. The offset is relative from the start of the file.
0x0058 4 DWORD The number of entries in section A.
0x005C 4 DWORD The offset to section B. The offset is relative from the start of the file.
0x0060 4 DWORD The number of entries in section B.
0x0064 4 DWORD The offset to section C. The offset is relative from the start of the file.
0x0068 4 DWORD Length of section C.
0x006C 4 DWORD Offset to section D. The offset is relative from the start of the file.
0x0070 4 DWORD The number of entries in section D.
0x0074 4 DWORD Length of section D.
0x0078 8  ? Unknown
0x0080 8 FILETIME Latest execution time (or run time) of executable (FILETIME)
0x0088 7 x 8 = 56 FILETIME Older (most recent) latest execution time (or run time) of executable (FILETIME)
0x00C0 16 ? Unknown
0x00D0 4 DWORD Execution counter (or run count)
0x00D4 4 ? Unknown
0x00D8 4 ? Unknown
0x00DC 88 ? Unknown

Section A - Metrics array

Metrics entry record - version 17

The metrics entry records – version 17 is 20 bytes in size and consists of:

Field Offset Length Type Notes
0 4 DWORD Start time in ms
4 4 DWORD Duration in ms
8 4 DWORD Filename string offset
The offset is relative to the start of the filename string section (section C)
12 4 DWORD Filename string number of characters without end-of-string character
16 4 DWORD Unknown, flags?

Metrics entry record - version 23

The metrics entry records – version 23 is 32 bytes in size and consists of:

Field Offset Length Type Notes
0 4 DWORD Start time in ms
4 4 DWORD Duration in ms
8 4 DWORD Average duration in ms?
12 4 DWORD Filename string offset
The offset is relative to the start of the filename string section (section C)
16 4 DWORD Filename string number of characters without end-of-string character
20 4 DWORD Unknown, flags?
24 8 NTFS file reference
0 if not set.

Metrics entry record - version 26

The metrics entry record – version 26 appears to be similar to metrics entry record – version 23.

Section B - Trace chains array

This section contains an array with 12 byte (version 17, 23 and 26) entry records.

Field Offset Length Type Notes
0 4 Next array entry index
Contains the next trace chain array entry index in the chain, where the first entry index starts with 0, or -1 (0xffffffff) for the end-of-chain.
4 4 Total block load count
Number of blocks loaded (or fetched)
The block size 512k (512 x 1024) bytes
8 1 Unknown
9 1 Sample duration in ms?
10 2 Unknown

Section C - Filename strings

This section contains filenames strings, it consists of an array of UTF-16 little-endian formatted strings with end-of-string characters (U+0000).

At the end of the section there seems to be alignment padding that can contain remnant values.

Section D - Volumes information (block)

Section D contains one or more subsections, each subsection refers to directories on a volume.

If all the executables and libraries referenced in the C section are from one single disk volume, there will be only one section in the D section. If multiple volumes are referenced by section C, section D will contain multiple sections. (A simple way to force this situation is to copy, say, NOTEPAD.EXE to a USB drive, and start it from that volume. The corresponding prefetch file will have one D header referring to, e.g. \DEVICE\HARDDISK1\DP(1)0-0+4 (the USB drive), and one to, e.g. \DEVICE\HARDDISKVOLUME1\ (where the .DLLs and other support files were found).

In this section, all offsets are assumed to be counted from the start of the D section.

Volume information

The structure of the volume information is version dependent.

Volume information - version 17

The volume information – version 17 is 40 bytes in size and consists of:

Field Offset Length Type Notes
VI1 +0x0000 4 DWORD Offset to volume device path (Unicode, terminated by U+0000)
VI2 +0x0004 4 DWORD Length of volume device path (nr of characters, including terminating U+0000)
VI3 +0x0008 8 FILETIME Volume creation time.
VI4 +0x0010 4 DWORD Volume serial number of volume indicated by volume string
VI5 +0x0014 4 DWORD Offset to sub section E
VI6 +0x0018 4 DWORD Length of sub section E (in bytes)
VI7 +0x001C 4 DWORD Offset to sub section F
VI8 +0x0020 4 DWORD Number of strings in sub section F
VI9 +0x0024 4  ? Unknown

Volume information - version 23

The volume information entry – version 23 is 104 bytes in size and consists of:

Field Offset Length Type Notes
VI1 +0x0000 4 DWORD Offset to volume device path (Unicode, terminated by U+0000)
VI2 +0x0004 4 DWORD Length of volume device path (nr of characters, including terminating U+0000)
VI3 +0x0008 8 FILETIME Volume creation time.
VI4 +0x0010 4 DWORD Volume serial number of volume indicated by volume string
VI5 +0x0014 4 DWORD Offset to sub section E
VI6 +0x0018 4 DWORD Length of sub section E (in bytes)
VI7 +0x001C 4 DWORD Offset to sub section F
VI8 +0x0020 4 DWORD Number of strings in sub section F
VI9 +0x0024 4  ? Unknown
VI10 +0x0028 28 ? Unknown
VI11 +0x0044 4 ? Unknown
VI12 +0x0048 28 ? Unknown
VI13 +0x0064 4 ? Unknown

Volume information - version 26

The volume information entry – version 26 appears to be similar to volume information – version 23.

Sub section E - NTFS file references

This sub section can contain NTFS file references.

For more information see Windows Prefetch File (PF) format.

Sub section F - Directory strings

This sub sections contains directory strings. The number of strings is stored in the volume information.

A directory string is stored in the following structure:

Field Offset Length Type Notes
0x0000 2 DWORD Number of characters (WORDs) of the directory name. The value does not include the end-of-string character.
0x0002 USTR The directory name as a Unicode (UTF-16 litte-endian string) terminated by an end-of-string character (U+0000).

See Also

External Links