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.
Press Alt-F2 to switch to the console.
List all available drives with the fdisk -l command. Use the sizes of the disks to pick out the thumbdrive.
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
Use the following command to dump the MBR, which is usually (but not always) the first sector of the hdadrive:
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
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
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
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.