Identifying GUID Partition Table (GPT)

Identifying GUID Partition Table (GPT) in this GPT header will help an investigator analyze the layout of the disk including the locations of the partition table, partition area, and backup copies of the header and partition table. Investigators can use cmdlets given below in Windows PowerShell to identify the presence of GPT:

Get-GPT

Get-GPT command helps investigator to analyze the GUID Partition Table data structure of the hard disk. It requires the use of the -Path parameter which takes the Win32 Device Namespace (ex.\\.\ PHYSICALDRIVE1) for the device from which it should parse the GPT.

In case, the investigator uses the Get-CPT on a disk formatted with a Master Boot Record, it will display an error message prompting to use Get-MBR instead.

Alternate Method:

• Open “Computer Management” application and click “Disk Management” on the left pane. Right-click on the primary disk (here, Disk 0) and then click Properties
• In the Device Properties window, click ‘Volumes” tab to see the Partition style

Related Product : Computer Hacking Forensic Investigator | CHFI

Identifying GUID Partition Table (GPT) (Cont’d)

1. Get-Boot Sector

The Get-BootSector is a command that can help the investigator parse GPTs of both types of hard disks including the ones formatted with either UEFI or MBR. This command acts as replacement for Get-MBR and Get-GPT cmdlets. Get-BootSector analyzes the first sector of hard drive and determines the formatting type used and then parses the hard drive GPT.

2. Get-PartitionTable

This command analyzes the GUID partition table to find the exact type of boot sector (Master Boot Record or GUID PartitionTable) and displays the partition object.

3. Analyzing the GPT Header and Entries

Most of the operating systems that support GPT disk access come up with a basic partitioning tool, which displays details about CPT partition tables. In windows tools such as DiskPart tool display the partition details, whereas MAC systems use the OS X Disk utility and Linux uses GNU parted tool.

Sleuthkit mmls command can help the investigators to view detailed partition layout for GPT disk along with the MAR details. Alternatively, investigators can gather details about GPT header and partition entries through manual analysis of disk drive using a hex calculation or editing tool called Hex editor.

Also Read : What is the Booting Process?

4. GPT Artifacts

Deleted and Overwritten GUID Partitions

Case 1: In hard disks, the conversion or repartition of the MBR disk to GPT will generally overwrite the sector zero with a protective MBR, which will delete all the information about the old partition table. The investigators should follow the standard forensics methods of searching the filesystems to recover data about the previous MBR partitioned volumes.

Case 2: When conversion or repartition of the GPT to MBR disk takes place, then the GPT header and tables may remain intact based on the tool used. Investigators can easily recover or analyze data of such disk partitions.

Implementation of general partition deletion tools for deletion of partition on the GPT disk might will delete the protective MBR only, which investigators can easily recreate by simply reconstructing the disk.

As per UEFI

 specification, if all the fields in a partition entry have zeroed values, it implies that the entry is not in use. In this case, data recovery about deleted GUID partition entries is not possible.

GUID Identifiers

• GPT scheme provides GLJIDs which are of investigative value as they are unique and hold potential information about entire disk and each partition within them
• GUIDs possess unique identifying information for both disks and individual partitions
• Investigators can use tools such as UUID to decode various versions of GLAD/UUID

5. Hidden Information on GPT Disks

Intruders may hide data on GPT disks as they do it on traditional MBR disks using a flexible and extensible disk partitioning schemes. Data hiding places on GPT disks may be inter-partition gaps, un-partitioned space towards the end of the disk, GPT header, and reserved areas. The other artifacts may include manipulated GPT headers that create place for hiding data, misplaced starting, and ending LBAs, as well as areas with reserved tag.
Current forensic methods and toots to perform GPT analysis are not satisfactory.

Questions related to this topic

1. Can you mix MBR and GPT drives?
2. What is the maximum disk size for a GPT based partition?
3. How do I change a partition from MBR to GPT?
4. Should I use MBR or GPT?

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