Acquiring Files

The WinPmem imager can also acquire multiple files into the AFF4 volume. These can be devices (such as disks using /dev/sda) or logical files.

Acquiring a disk image

     WinPmem.exe -i \\.\c: -o output.aff4 -dd

Note that by default the aff4 imager will append new streams to the output volume if it already exists. This is useful for appending more relevant evidence after the initial acquisition is completed. If you dont want this behaviour you can specify the -t (–truncate) flag to truncate the output volume before adding the new stream.

Acquiring multiple logical files

     WinPmem -i C:/Windows/*.exe -o output.aff4

Using glob expressions as input files will be expanded as required to include all filenames matching the globs. This works also on Windows which does not expand globs on the shell.

Acquiring files newer than 30 days can be done by using the find

command on Linux or Powershell script on Windows.

     find /usr/bin/ -ctime -30 | WinPmem -i @ -o /tmp/output.aff4

Or on Windows:

     powershell -Command "Get-ChildItem f:\ | Where{$_.LastWriteTime -gt
        (Get-Date).AddDays(-7)} | SELECT Name | ft -hidetableheaders" |
        WinPmem -i @ -o /tmp/output.aff4

Using a single @ as the input filename, makes the aff4 imager read the list of files to acqiure from stdin. This allows for more sophisticated pre-processing and makes it easier to acquire files with spaces or special characters in their names (without having to worry about shell escapes). In the above example we use the find unix command to identify files newer than 30 days and also add them to the image.

Enabling multiple threads

     WinPmem.exe -o /tmp/output.aff4 --threads 6

The aff4 imager uses a single thread by default, but if your machine has more cores, then you will see vastly better performance by allowing more threads to run. This is particularly important when using the default compression of the zlib compressor which needs more CPU resources.

Enabling snappy compression

     WinPmem.exe -o output.aff4 --compression snappy

The Snappy compression engine is much faster than the default zlib but trades off compression size. Enabling snappy compression will result in slightly larger images but should complete faster.

Splitting an image into multiple volumes

     WinPmem.exe -o output.aff4 --split 650m

Some images are very large. By enabling splitting images it is possible to restrict the maximum size of each volume. The imager will close off each volume as it is done with it, and so you can start uploading, archiving each volume as soon as it is finished. Note that the same stream may be split across one or more volumes so you will need all volumes to properly extract the stream.

Acquiring into standard output

     WinPmem.exe -o - | gsutil cp - gs://rekall-test/test.aff4

If the output filename is specifies as a single dash (“-”), the imager writes the AFF4 volume to stdout. This allows the image to be piped to a different tool. The example above streams the image directly to a cloud storage bucket without needing to write a temporary local copy.