Support article

Summary

This article explains how you can collect an MBR rootkit sample for F-Secure Labs to analyse. Before performing any of the steps, you will need:

• a USB drive (or other similar removable media)
• F-Secure Rescue CD 3.0

Collecting an MBR rootkit sample

To collect an MBR rootkit sample, do as follows

1. Insert the thumbdrive to the powered-down system. Boot from F-Secure Rescue CD and let it initialize until the screen presents the choice to continue or restart the computer.
2. Press Alt-F2 to switch to the console.
3. List all available drives with the fdisk -l command. Use the sizes of the disks to pick out the thumbdrive.
4. Mount the thumbdrive with the following command:

   mount %devicename%
   where %devicename% = the name of the thumbdrive
   
   Example:
   Name of thumbdrive: /dev/sdc1
   Command: mount /dev/sdc1

5. Use the following command to dump the MBR, which is usually (but not always) the first sector of the hda drive:

   dd if=%device_name% of=%filename% bs=512 count=1
   where %device_name% = name of the device and %filename% = name of the output dump
   
   Example:
   Name of the output dump: /tmp/mbr_disk
   Command: dd if=/dev/hda of=/tmp/mbr_disk bs=512 count=1

6. You may also use the above command to dump the first sector of other drives, if you feel the information may be relevant.
   Note: Ensure the name of the output dump is changed to avoid overwriting the dumped MBR information.
   
   Example:
   Name of the output dump: /tmp/mbr_disk1
   Command: dd if=/dev/hda1 of=/tmp/mbr_disk1 bs=512 count=1
   
   
7. Copy the dumped information to the thumbdrive with the following command: cp %name of output dump% %file on thumbdrive%

   You can determine the path to the thumbdrive by typing the df command and noting the relevant entry in the "mounted on" column.

   Example:
   cp /tmp/mbr_disk /media/shc1/mbr_disk

8. Use an uncompromised machine to submit all the dumped files to F-Secure via the Sample Analysis System , along with any relevant details. The dumped files may also be sent in as an attachment to a reply for an existing SAS case.