Understanding the audit process

Understanding the audit process

Information system security compliance is reliant on the completion of two foundational processes:

Implementation and operation of security controls
Aligning the information system with in-scope standards and regulations involves internal tasks which must be conducted before a formal assessment. Auditors may be involved at this state to conduct gap analysis, provide guidance, and increase the likelihood of successful certification.
Independent verification and validation
Demonstration to a neutral third-party that system security controls are implemented and operating effectively, in compliance with in-scope standards and regulations, is required before many information systems achieve certified status. Many certifications require periodic audits to ensure continued certification, considered part of an overarching continuous monitoring practice.

Determining audit scope

Determining audit scope, specifically what controls are needed and how to design or modify an OpenStack deployment to satisfy them, should be the initial planning step.

When scoping OpenStack deployments for compliance purposes, prioritize controls around sensitive services, such as command and control functions and the base virtualization technology. Compromises of these facilities may impact an OpenStack environment in its entirety.

Scope reduction helps ensure OpenStack architects establish high quality security controls which are tailored to a particular deployment, however it is paramount to ensure these practices do not omit areas or features from security hardening. A common example is applicable to PCI-DSS guidelines, where payment related infrastructure may be scrutinized for security issues, but supporting services are left ignored, and vulnerable to attack.

When addressing compliance, you can increase efficiency and reduce work effort by identifying common areas and criteria that apply across multiple certifications. Much of the audit principles and guidelines discussed in this book will assist in identifying these controls, additionally a number of external entities provide comprehensive lists. The following are some examples:

The Cloud Security Alliance Cloud Controls Matrix (CCM) assists both cloud providers and consumers in assessing the overall security of a cloud provider. The CSA CMM provides a controls framework that map to many industry-accepted standards and regulations including the ISO 27001/2, ISACA, COBIT, PCI, NIST, Jericho Forum and NERC CIP.

The SCAP Security Guide is another useful reference. This is still an emerging source, but we anticipate that this will grow into a tool with controls mappings that are more focused on the US federal government certifications and recommendations. For example, the SCAP Security Guide currently has some mappings for security technical implementation guides (STIGs) and NIST-800-53.

These control mappings will help identify common control criteria across certifications, and provide visibility to both auditors and auditees on problem areas within control sets for particular compliance certifications and attestations.

Phases of an audit

An audit has four distinct phases, though most stakeholders and control owners will only participate in one or two. The four phases are Planning, Fieldwork, Reporting and Wrap-up. Each of these phases is discussed below.

The Planning phase is typically performed two weeks to six months before Fieldwork begins. In this phase audit items such as the timeframe, timeline, controls to be evaluated, and control owners are discussed and finalized. Concerns about resource availability, impartiality, and costs are also resolved.

The Fieldwork phase is the most visible portion of the audit. This is where the auditors are onsite, interviewing the control owners, documenting the controls that are in place, and identifying any issues. It is important to note that the auditors will use a two part process for evaluating the controls in place. The first part is evaluating the design effectiveness of the control. This is where the auditor will evaluate whether the control is capable of effectively preventing or detecting and correcting weaknesses and deficiencies. A control must “pass” this test to be evaluated in the second phase. This is because with a control that is designed ineffectually, there is no point considering whether it is operating effectively. The second part is operational effectiveness. Operational effectiveness testing will determine how the control was applied, the consistency with which the control was applied and by whom or by what means the control was applied. A control may depend upon other controls (indirect controls) and, if they do, additional evidence that demonstrates the operating effectiveness of those indirect controls may be required for the auditor to determine the overall operating effectiveness of the control.

The Reporting phase is where any issues that were identified during the Fieldwork phase will be validated by management. For logistics purposes, some activities such as issue validation may be performed during the Fieldwork phase. Management will also need to provide remediation plans to address the issues and ensure that they do not reoccur. A draft of the overall report will be circulated for review to the stakeholders and management. Agreed upon changes are incorporated and the updated draft is sent to senior management for review and approval. Once senior management approves the report, it is finalized and distributed to executive management. Any issues are entered into the issue tracking or risk tracking mechanism the organization uses.

The Wrap-up phase is where the audit is officially spun down. Management will begin remediation activities at this point. Processes and notifications are used to ensure that any audit related information is moved to a secure repository.

Internal audit

Once a cloud is deployed, it is time for an internal audit. This is the time to compare the controls you identified above with the design, features, and deployment strategies utilized in your cloud. The goal is to understand how each control is handled and where gaps exist. Document all of the findings for future reference.

When auditing an OpenStack cloud it is important to appreciate the multi-tenant environment inherent in the OpenStack architecture. Some critical areas for concern include data disposal, hypervisor security, node hardening, and authentication mechanisms.

Prepare for external audit

Once the internal audit results look good, it is time to prepare for an external audit. There are several key actions to take at this stage, these are outlined below:

  • Maintain good records from your internal audit. These will prove useful during the external audit so you can be prepared to answer questions about mapping the compliance controls to a particular deployment.
  • Deploy automated testing tools to ensure that the cloud remains compliant over time.
  • Select an auditor.

Selecting an auditor can be challenging. Ideally, you are looking for someone with experience in cloud compliance audits. OpenStack experience is another big plus. Often it is best to consult with people who have been through this process for referrals. Cost can vary greatly depending on the scope of the engagement and the audit firm considered.

External audit

This is the formal audit process. Auditors will test security controls in scope for a specific certification, and demand evidentiary requirements to prove that these controls were also in place for the audit window (for example SOC 2 audits generally evaluate security controls over a 6-12 months period). Any control failures are logged, and will be documented in the external auditors final report. Dependent on the type of OpenStack deployment, these reports may be viewed by customers, so it is important to avoid control failures. This is why audit preparation is so important.

Compliance maintenance

The process doesn’t end with a single external audit. Most certifications require continual compliance activities which means repeating the audit process periodically. We recommend integrating automated compliance verification tools into a cloud to ensure that it is compliant at all times. This should be in done in addition to other security monitoring tools. Remember that the goal is both security and compliance. Failing on either of these fronts will significantly complicate future audits.

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