Secure disposal of IT - public and private cloud
This document is the Ministry of Justice (MoJ) IT Disposal of Equipment Guidance covering:
Data sanitisation and deletion within a public or private cloud environment that a Service Provider hosts.
It is designed to ensure the confidentiality of MoJ data remains when a cloud service is decommissioned.
This information is part of the MoJ asset management policies and guidance on media handling.
Note: For disposal of physical on-premise media and data, refer to the Secure disposal of IT - physical and on-premise guidance.
Parent topic: Secure disposal of IT equipment
MoJ cloud environments overview
The MoJ consumes several public (shared cloud) and private cloud platforms, operating over 900 different technology systems ranging from internal IT tools or solutions to case management solutions.
Public cloud service environments are delivered through the internet. They are shared across organisations using a “multi-tenant” model. For example, a service provider hosts a public environment that gives the MoJ and other customers a portion of the same physical server hardware to run their website or application.
Private cloud environments differ, as they are dedicated to a single tenant. They are intended to address concerns on data security. They may also offer greater control because resources are not shared with other tenants.
Public and private clouds both have different ways of ensuring compliance. Therefore, compliance should be evaluated using the government’s Cloud Security Principles. In addition, these principles should be assessed against several other factors outlined in the government’s technical guidance on securing your cloud environment.
NCSC on sanitisation and disposal of cloud assets
MoJ asset owners or administrators should be confident that:
All data stored in a cloud service are erased when resources are moved or re-provisioned, when the resources are no longer required, or when the asset owner requests or carries out the erasure of the data.
Storage media that has held MoJ data is sanitised or securely destroyed at the end of its life.
Note: For more information on this approach, refer to NCSC guidance on the sanitisation of cloud assets.
MoJ asset owners or administrators shall ensure that for all data stored in a cloud service:
All equipment containing MoJ data, credentials, or configuration information for the service is identified at the end of its life and before it is recycled.
Any components containing sensitive data are sanitised, removed, or destroyed.
Accounts or credentials specific to redundant equipment are revoked to reduce their value to an attacker.
Note: For more information on this approach, refer to NCSC guidance on equipment disposal.
Checklist for the sanitisation and disposal of cloud assets
Due to the possible lack of control of physical infrastructure, a checklist of questions to ask a cloud provider to establish a baseline for data sanitisation and deletion is provided.
|Reference||Action to help ensure sufficient data sanitisation and deletion with a cloud provider|
|1.||A standardised process to be agreed including credible witnesses, describing how private/public cloud service providers store and handle hard disks for decommissioning until destruction. This shall be aligned to the following controls as outlined in ISO 27002: 8.3.1 - Management of removable media (Control) “Procedures should be implemented for the management of removable media in accordance with the classification scheme adopted by the organization.” 11.2.7 - Secure Disposal or re-use of equipment (Control) “All items of equipment containing storage media should be verified to ensure that any sensitive data and licensed software has been removed or securely overwritten prior to disposal or re-use.”|
|2.||Standardised procedures agreed between the MoJ and the Cloud Provider to establish a chain of custody including crypto-shredding or an initial software erasure and then degaussing the disk and/or shred/incinerate/pulverise. This shall be aligned to the following control as outlined in ISO 27002: 8.3.2 - Disposal of media (Control) “Media should be disposed of securely when no longer required, using formal procedures.”|
|3.||If required, the cloud provider agrees they shall securely deliver in transit hard disks that contain MoJ data, which the MoJ shall destroy.|
|4.||Optionally, MoJ asset owners using the responses to checklists 1 to 3 can establish a data sanitisation strategy SLA aligned to Data Security Lifecycle Management standards, specifically sanitisation and destruction (end of life).|
Note: The Data Security Lifecycle Management concept is described in the Cloud Security Alliance’s Security Guidance for Critical Areas of Focus in Cloud Computing v4.0 (CCA CSM v4.0). Refer to section 5.1.2: The Data Security Lifecycle on page 62.
Note: To ensure that MoJ data in the cloud is sanitised sufficiently and that the devices or hard drives they are stored in meet data management security standards when destroyed, it might require specific clauses in the contract with the cloud provider.
Note: If the cloud provider has a mechanism for resilience or redundancy that duplicates MoJ data, this duplicated data shall also be sanitised or destroyed using the checklist provided. All duplicated data shall be sanitised at the same time. The MoJ destroys all decryption keys held in their possession to ensure this occurs. This makes all the duplicated cloud data unreadable. This method is called crypto-shredding.
When duplicates of data cannot be destroyed immediately, there shall be methods in place for protecting and controlling the data until data destruction is assured. This includes the supplier providing a formal declaration of destruction. If any destruction tasks are delayed, a confirmation date of final data destruction shall be provided.
Data deletion - Verification for virtual devices and SAN allocations (public cloud or on-prem)
When working on an MoJ public cloud or on-premise virtual infrastructure, obtaining a decommissioning or destruction certificate cannot be carried out according to the method used for the MoJ’s on-premise physical servers and disk arrays when they are wiped, blanked, destroyed, or overwritten. This is because these MoJ infrastructures might be needed to support other services or infrastructure still in use.
For example, a single on-premise physical server might host eight virtual servers providing various services. If three of these virtual servers are deleted, the other five need to continue to operate. Similarly, an on-premise firewall might have a virtual context or a subset of rules that need to be removed, but the physical equipment is still required to provide services to other devices.
A soft and hard decommissioning approach for MoJ on-prem virtual devices might also be required. A soft decommissioning involves switching off the resource, ensuring that it cannot restart on a scheduled basis. This means stopping all hosted service or application, powering down the resource, and setting any remaining firewall rules to block all traffic to or from the resource. Once this soft decommissioning is complete, a hard decommissioning can take place. Hard decommissioning involves deleting the configuration, images, and storage that the virtual devices used and returning the resources to a resource pool.
The process used for SAN or VM items destruction and decommissioning is described next.
Install a screen recording tool on the operator’s terminal. In cases where it is impossible to install a recording tool on a device, screenshots showing before and after states are acceptable if agreed in advance.
Ideally, have a witness sit next to the operator and start the screen recording tool. If this is not possible, the witness can view the screen recording after the decommissioning activity.
Encryption keys for the solution should be archived for backup retention purposes, if necessary, onto a secure storage space.
For each of the given technologies, the operator should create an initial listing of the resource, then run the decommissioning task, then finish by creating another listing to show that the change has occurred.
Depending on the process used to create or maintain backups, some jobs might need to be removed. However, backups should not be deleted without consulting the retention policy and confirming that deletion is compliant with policy. This check applies to all decommissioning steps.
The operator, if possible, formats the SAN areas used for the files and “zero’s” them by overwriting all storage with binary 0 data. The operator then deletes the various SAN LUNs, Arrays, Volumes, and other storage units in the SAN. Each of the storage units is reallocated to free space. This is then verified with listings of the SAN structure.
Any virtual machines are permanently deleted in the virtual machine control panel. An attempt should be made to list and restart the machine; this should provide evidence that the virtual machine has been permanently removed.
Any firewall or other Security Enforcing Functionality (SEF) configurations should be removed from the live service.
Any switch configurations, such as IP addresses or subnet masks, should be removed.
Screen recording is stopped.
Witness signs the decommissioning certificate, and the screen recording is stored in a secure storage space.
Note: There are free versions of screen recorder tools that might be used. The tool shall be assessed, before use, by requesting an MoJ security team review using this form. Refer to the MoJ guidance on requesting that an app be approved for use. An alternative option would be to use Teams to record the decommissioning via screen share.
For any further questions or advice relating to security, contact: firstname.lastname@example.org.
If you have any questions or comments about this guidance, such as suggestions for improvements, please contact: email@example.com.