Keeping Legacy Apps Secure During Cloud Migrations

Migrating your organization’s legacy applications to the cloud is a critical step for modernizing.

Your operation can come with significant security challenges because of its outdated nature. Legacy systems lack modern security features, often have hidden dependencies, or rely on insecure connections that don’t translate well to cloud environments.

For this reason, cloud migration becomes a delicate balance between speed and finesse. To maintain the continuity of your organization, you may need to use ring-fencing techniques and network controls to guarantee success. Here, we explore that with practical CLI snippets and conceptual diagrams to demonstrate how you can use these approaches in your cloud migrations.

Ring Fencing and Why it Matters

Ring fencing isolates legacy applications from the rest of your network, reducing their attack surface without requiring disruptive updates or rewrites. Think of it as creating a protective barrier around legacy applications to limit their interactions with other systems and exposure to unauthorized access and potential lateral movement by attackers.

Using ring fencing on your legacy applications is essential, especially when modernizing your IT infrastructure. Your legacy applications need ring fencing because:

• Some legacy applications with outdated tech stacks may lack critical patches to known exploits.
• You may need ring fencing during cloud migrations to stay compliant with government regulations, including GDPR, HIPAA, or ISO/IEC 27001.
• Cloud migrations can often expose your application to internet-based threats, unlike on-premise environments protected by your firewalls.
• Hidden dependencies on other systems can break during cloud migration, exposing previously unknown security gaps.

Ring-Fencing Techniques for Legacy Applications

With proper ring fencing, you can isolate and protect business systems and ensure business continuity and compliance while minimizing cybersecurity risks. Here are some techniques and code samples you can explore to protect your systems:

Microsegmentation

This technique breaks the network down into smaller segments, restricting application access to only necessary resources. It allows only necessary communications between the legacy app and approved systems. In case of a breach, microsegmentation mitigates the impact of a breach by isolating the legacy app from other systems.

Data Isolation

Data Isolation uses secure vaults to store sensitive configuration data, like database credentials. Doing this limits your legacy apps from directly accessing these credentials in case of exposure to a cyber threat.

Application Containment

Using this technique, you control what an application can do once running. Application containment prevents a legacy application from interacting with unauthorized processes or resources. This way, you prevent attackers from weaponizing legitimate tools, enhancing security during migration.

Identity-Based Access Control

You can replace legacy security mechanisms with modern role-based access control (RBAC) using identity providers. Using RBAC, for instance, enforces least privilege, reducing the risk of unauthorized access by attackers in case of a breach during your migration process. Only authorized users or services can access the legacy app during migration.

Network Controls for Legacy Systems (With CLI examples)

Using network controls is a simple but powerful way to guarantee security for your legacy systems. It manages traffic flow in your networks, enforces access policies, and monitors activity. Below are key network control strategies:

Configure Your Virtual Private Cloud (VPC)

Setting up a VPC with private subnets can help you with the public internet exposure of your legacy apps. Create Network Access Control Lists (NACLs) that filter network traffic, allowing your legacy apps to communicate with specific endpoints. Network security groups also work similarly.

Zero-Trust Architecture

With this type of architecture, the network system assumes no trust for any entity or user, requiring continuous verification for access. You can use zero-trust architecture both on-premises and cloud resources, particularly reducing risks during migrations done in phases.

Using a dedicated network firewall and VPC endpoints can enforce this model, protecting your hybrid system against lateral movement attacks. Add web filtering at the DNS layer to block malicious or unauthorized domains, preventing legacy apps from connecting to harmful endpoints during migration.

Secure Connectivity for Hybrid Environments

Use Virtual Private Networks (VPNs) to securely connect on-premises systems to cloud resources. VPNs ensure secure communication for apps relying on on-premises databases. You can also use AWS Direct Connect to maintain security during migration phases, especially for complex legacy systems.

Monitoring and Logging

Additionally, you can set up real-time monitoring with tools like AWS CloudTrail and Amazon CloudWatch to detect unauthorized access or anomalies. Keeping logs also helps you identify suspicious activity during migration, giving you a chance to take action. It also ensures you stay compliant with data safety regulations, with a quick response to any security incidents within your legacy apps.

Conceptual Diagram of Ring Fencing Legacy Apps

Below is a textual representation of a network architecture for securing a legacy application during cloud migration:

Best Practices and Considerations for Migrating Legacy Applications

You can never be too cautious when securing your legacy applications before migration to the cloud. To further enhance security, here are some more ideas to consider:

• Conduct a pre-migration assessment with dependency mapping and security audits to identify any potential vulnerabilities created before or during the migration process. Doing that helps you plan better for security incidents that may occur at the start of your migration.
• Use a phased approach to your migration process. Start by moving non-critical components to the cloud, testing all controls. Additionally, you can use a hybrid approach for continuity in your business.
• Modernize Some Applications Before Migration. Where possible, update and refactor critical components of your legacy apps to ensure cloud compatibility, avoiding “lift-and-shift” without updates..
• Where possible, partner with experts, cloud migration specialists, especially if you run a large organization with complex systems or mainframes.