Understanding Cloud Security Zones for Korean Government and Public Institutions

How Network Separation and System Criticality Determine the Appropriate Cloud Zone

One-Line Summary

Korean government and public institutions should determine the appropriate cloud zone based on network connectivity and system criticality before selecting and implementing a cloud service.

1. Why Cloud-Zone Classification Matters

Cloud adoption in government and public institutions is not simply a matter of selecting a cloud provider.

Security requirements must be considered together with:

Internal and Internet network separation
System criticality
Data protection
Physical and logical separation
Security monitoring
Incident investigation
Disaster recovery

The National Cloud Computing Security Guidelines (January 2023) classify cloud environments for government and public institutions into three major zones:

Public Business Network Zone
Public Internet Network Zone — Physical Separation
Public Internet Network Zone — Logical Separation

The appropriate zone is selected according to the criticality level of the system.

2. Start With Network Separation

Korean government and public institutions traditionally separate their business networks (internal networks) from Internet networks (external networks) to reduce the risk of unauthorized access and information leakage.

Cloud environments follow the same basic principle.

In simple terms:

Cloud connected to a business network → Public Business Network Zone

Cloud connected to an Internet network → Public Internet Network Zone

The guidelines explain that a cloud connected to an institution's business network should be treated as part of that business network, while a cloud connected to its Internet network should be treated as part of the Internet network.

3. The Three Cloud Zones

3.1 Public Business Network Zone

The Public Business Network Zone is a cloud environment connected to an institution's internal business network.

It may be located in:

A cloud center built and operated by the institution
A data center operated by an integrated management organization
A private-sector cloud center dedicated to public business networks

One of its most important characteristics is that it has no direct connection point to the Internet.

The public business network zone is also physically separated from commercial user service zones and physically separated from the public Internet network zone.

Applicable system criticality

Systems with high, medium, or low criticality may be located in this zone.

This makes the zone particularly important when highly sensitive internal government systems are being considered for cloud migration.

4. Public Internet Network Zone — Physical Separation

The second type is the Public Internet Network Zone with physical separation.

This zone is connected to an institution's Internet network.

Typical examples may include:

Public websites
Citizen-facing online services
Internet-facing services
Systems that require Internet connectivity

The public Internet zone must be physically separated from commercial user service areas and physically separated from the public business network zone.

Applicable system criticality

The guidelines allow systems with medium or low criticality to be located in this zone.

5. Public Internet Network Zone — Logical Separation

The third type is the Public Internet Network Zone with logical separation.

Instead of building a completely separate physical infrastructure, virtualization and network technologies are used to logically separate the public-sector environment from commercial user environments.

Technologies may include:

Server virtualization
Network virtualization
Hypervisors
NFV
SDN

However, there is a significant restriction.

Logical separation is allowed only for low-criticality systems

The guidelines specify that logical zone separation is permitted only for systems classified as low criticality.

Therefore, an institution should determine the system's criticality before accepting a logically separated cloud environment from a provider.

6. Comparing the Three Zones

Item	Public Business Network	Public Internet — Physical	Public Internet — Logical
Network	Business network	Internet network	Internet network
Separation from commercial users	Physical	Physical	Logical
System criticality	High / Medium / Low	Medium / Low	Low
Direct Internet connection	No	Yes	Yes
Typical use	Internal business systems	Public-facing Internet services	Lower-criticality Internet services
Management	Domestic	Domestic	Domestic

The most important relationship is between system criticality and cloud-zone eligibility.

A simplified way to understand the framework is:

High → Public Business Network Zone

Medium → Public Business Network or Physically Separated Public Internet Zone

Low → Public Business Network, Physically Separated Public Internet Zone, or Logically Separated Public Internet Zone

The actual implementation should also consider the system architecture, data characteristics, interconnections, and applicable security requirements.

7. What Does “Zone Separation” Really Mean?

Zone separation is not simply a matter of placing servers in different locations.

The guidelines describe zone separation as a protective measure designed to prevent interference between government cloud services and general-user cloud services in terms of data and processes, while maintaining the environment required for security monitoring, incident investigation, and preventive security activities.

Zone separation may be implemented through:

Physical separation
Logical separation

For systems of high, medium, and low criticality, physical separation from general-user service areas is used where required. Logical separation is restricted to low-criticality systems.

8. Physical vs. Logical Separation

Physical Separation

Physical separation means that government/public-sector cloud resources and general commercial-user resources are physically separated.

Resources that may require separation include:

Servers
Networks
Security devices
Access-control facilities
Operational environments
Operating personnel

The guidelines require physical separation from general-user service areas for systems to which the relevant physical-separation requirements apply.

Logical Separation

Logical separation uses virtualization and networking technologies to create isolated virtual environments.

Because logical separation depends heavily on virtualization and access-control mechanisms, vulnerabilities that could compromise the separation must be prevented, mitigated, or removed, and unauthorized access must be monitored.

9. Common Security Principles

The cloud-zone decision is only the beginning.

The guidelines also establish common security principles applicable to cloud environments.

Domestic location

All components required to operate the cloud service should be located in Korea, including:

Data servers
Management and operation servers
Authentication servers
Log servers
Backup servers

The guidelines also specify that these facilities should be under the exclusive legal jurisdiction of the Republic of Korea.

Domestic management

Management and operation should be performed by a management entity located in Korea.

Verified cryptographic modules

Verified cryptographic modules, such as KCMVP-validated modules, should be used for relevant access and data encryption.

Dedicated or encrypted communications

Dedicated lines or encrypted communications such as VPN should be used for cloud access.

Multi-factor authentication

MFA should be applied to cloud access and authentication.

Institution and service separation

Institutions and services should be separated within the cloud service area.

Security monitoring and incident response

The environment should support security monitoring, incident investigation, and preventive security activities.

Standard operating procedures

SOPs should cover backup, emergency recovery, change management, and incident response.

10. What Should Public-Sector IT Managers Check?

When evaluating a cloud proposal, the following questions are useful.

1. What is the system?

Identify the exact system and business function being migrated.

2. What is its criticality?

Determine whether the system is classified as:

High
Medium
Low

3. Which network is it connected to?

Determine whether the system belongs to:

Business network
Internet network

4. Which cloud zone is permitted?

Select among:

Public Business Network Zone
Public Internet Network Zone with Physical Separation
Public Internet Network Zone with Logical Separation

5. How is the cloud provider separating public-sector and commercial environments?

Check whether separation is physical or logical and how it is implemented.

6. Where are the data and supporting systems located?

Check:

Data
Logs
Backups
Authentication
Management systems

7. Who manages the environment?

Confirm the management structure and location.

8. Can the institution conduct security monitoring and incident investigation?

This is particularly important when using a commercial cloud provider.

11. Common Misunderstandings

“Commercial cloud automatically means Internet cloud.”

Not necessarily.

The guidelines include private-sector cloud centers dedicated to public business networks as possible locations for the Public Business Network Zone.

Therefore:

Commercial cloud provider ≠ automatically Internet cloud zone

These are separate concepts.

“Logical separation can be used for any system.”

No.

The guidelines restrict logical separation to low-criticality systems.

Therefore, system criticality must be determined before selecting this architecture.

“The same data center means there is no separation.”

Not necessarily.

A data center can host different cloud environments, provided that the required physical or logical separation mechanisms and security controls are properly implemented.

12. A Practical Cloud-Zone Decision Process

For a government or public-sector cloud project, the following sequence is useful:

Step 1 — Identify the system

↓

Step 2 — Determine system criticality

↓

Step 3 — Identify network connectivity

↓

Step 4 — Determine the permitted cloud zone

↓

Step 5 — Verify physical/logical separation

↓

Step 6 — Verify security monitoring and incident response

↓

Step 7 — Select a cloud service that satisfies the requirements

This approach prevents an organization from choosing a cloud service first and trying to fit the system into its architecture afterward.

13. Practical Checklist

Area	Questions
System criticality	High, medium, or low?
Network	Business or Internet network?
Cloud zone	Which of the three zones applies?
Separation	Physical or logical?
Commercial users	How are commercial-user resources separated?
Data location	Are data, logs, and backups located domestically?
Management	Is the environment managed domestically?
Authentication	Is MFA implemented?
Encryption	Are validated cryptographic modules used where required?
Network security	Dedicated line or encrypted communication?
Monitoring	Can the institution integrate security monitoring?
Incident response	Can incidents be investigated and responded to?
Recovery	Are backup and disaster-recovery procedures established?
Operations	Are SOPs established?

14. The Key Is Not “Which Cloud?” but “Which Zone?”

For government and public institutions, cloud adoption should ideally start with the following questions:

What system are we moving?

↓

How critical is the system?

↓

Which network does it belong to?

↓

Which cloud zone is appropriate?

↓

What type of separation is required?

↓

Does the provider satisfy the security requirements?

Only after these questions have been answered should the organization move to the final selection of a cloud service.

The 2023 revision is particularly important because it added system-criticality classification procedures and security requirements by cloud zone, making the relationship between system importance and cloud architecture more explicit.

15. Conclusion

The “Cloud Zone Classification” section of the National Cloud Computing Security Guidelines (January 2023) provides an important framework for government and public-sector cloud adoption.

The key points are:

Cloud environments are classified according to business-network and Internet-network connectivity.
System criticality determines which cloud zones can be used.
Government/public-sector cloud environments must be appropriately separated from general commercial-user environments.
Logical separation is limited to low-criticality systems.
Domestic location, domestic management, encryption, MFA, security monitoring, incident response, backup, and recovery must also be considered.

For public-sector IT managers, the practical lesson is simple:

Do not start with “Which cloud provider should we use?” Start with “Which cloud zone is appropriate for this system?”

Once the appropriate zone has been identified, the cloud provider and service architecture can be evaluated against the applicable security requirements.

This article is an original explanatory work based on the National Cloud Computing Security Guidelines (January 2023) and related public-sector materials. It paraphrases and reorganizes the source material rather than reproducing source text. For an actual project, the latest applicable regulations, institutional security requirements, and current guidance should be checked before implementation.