Virtel Blog - Mainframe modernization and security

5 Reasons to Replace Your TN3270 Terminal Emulator NOW

Written by Sebastian DEWAR | Mar 12, 2025 3:14:10 PM

TN3270 terminal emulators have long been a staple for accessing mainframe applications. However, as technology evolves and security concerns grow, it's becoming increasingly clear that traditional thick-client TN3270 emulators are no longer the optimal solution. This article explores five compelling reasons why organizations should consider replacing their existing TN3270 emulators with a modern, two-tier, total web-based alternative.

1. Enhanced Security and Compliance

There are two major ways to improve mainframe application security. One is by eliminating the inherent security issues traditional TN3270 emulators pose; the other is by utilizing more secure mainframe access methods though the implementation of Multi-Factor Authentication, Single Sign-on, and Identity Access Management solutions.

Modern, total web-based emulators offer improved security features, reducing the attack surface and providing better protection for sensitive mainframe data.

📌TN3270 Risks

Traditional TN3270 emulators have several significant security vulnerabilities that can expose organizations to various risks. The main security vulnerabilities include:

▶️Exposed Terminal Emulation Code:

Thick-client emulators often rely on code components, typically written in Java, running on server or user devices. This exposed code can be compromised and exploited by attackers and used for unauthorized access to mainframe applications.

▶️Reliance on Outdated Browsers:

Many legacy TN3270 emulators depend on Java and Java plugins, which are no longer supported by modern browsers. This reliance on outdated technology increases security risks.

▶️Expose Unaudited Macros:

Unaudited, user-developed TN3270 macros in thick-client emulators can pose a significant security threat, as they may contain unencrypted login credentials or submit numerous transactions without proper oversight.

▶️Unencrypted Login Credentials: 

These macros may store sensitive information, such as mainframe login credentials, in plain text. If a workstation hosting such macros is compromised, attackers can easily access this information and gain unauthorized entry to mainframe systems.

▶️Automated Macro Transactions:

Macros can execute large numbers of transactions, such as submitting multiple CICS (Customer Information Control System) transactions from external sources like Excel spreadsheets. This can lead to runaway CPU processing or unintentional data exposure if the macro is exploited or misused.

▶️Lack of Access Audit Trail:

Many legacy TN3270 emulators do not log the origin or end-user identification of accessed 3270 applications, making it difficult to trace unauthorized access or cyber attacks.  This not only inhibits the ability to trace unauthorized access, but does not provide the necessary evidence for security incidents when data loss, alteration or theft occurs or identify patterns of suspicious behavior or potential security threats in a timely manner.

▶️Exposed 3270 Fields:

In traditional emulators, 3270 screen field settings (hidden, protected, or unprotected) are enforced by code running on the user device. If compromised, attackers may be able to view hidden fields or modify protected fields.

▶️VPN-Dependent Encryption:

Relying on VPNs for security can inadvertently expose other IT systems and assets to unauthorized access, especially when only needing to provide third party access to specific, well-controlled mainframe applications.

These vulnerabilities highlight the need for organizations to consider a modern alternative that addresses these security concerns and provides more robust protection for mainframe resources.

📌Implementing Modern Security Practices

The days of using an 8-digit, case-insensitive userid and password are numbered.  Today’s digital landscape won’t allow such archaic practices.  Advanced security solutions are designed to seamlessly integrate with existing infrastructure and provide a fortified gateway between your legacy systems and modern web environments.

▶️End-to-End Encryption:

leverages the AT-TLS layers of the z/OS system, ensuring encrypted connections that comply with FIPS 140.2 and TLS 1.3 standards. This guarantees that your mainframe data remains secure while in transit, protecting it from external threats and ensuring compliance with the latest security protocols.

▶️Support PassTicket Generation:

enable secure, token-based authentication across the mainframe without requiring users to re-enter passwords. 

▶️LU Name Assignment:

expanded control over session management, allowing administrators to assign Logical Unit (LU) names based on user IDs, IP addresses, or other criteria.  This provides detailed oversight of user interactions and improves the ability to enforce security policies at every level of access.

▶️z/MFA Integration:

Boost security by integrating with z/OS MFA. This multi-layered approach ensures that users are verified not only by something they know (like a password) but also through something they have or are (like a mobile device or fingerprint).

▶️SSO Integration:

strengthen access control with SSO integration, by enabling SSO for your 3270 applications that seamlessly connect with solutions supporting SAML or OIDC.

 

2. Simplified Maintenance and Administration

Replacing thick-client TN3270 emulators with web-based alternatives can significantly reduce the maintenance and administration costs associated with providing secure mainframe access.

✅Elimination of Client-Side Installations:

These emulators are installed directly on the mainframe and accessed through standard web browsers, eliminating the need for individual installations on server or user workstations

✅Centralized Updates:

All maintenance and updates can be performed centrally on the mainframe, ensuring consistent functionality across all users without the need for individual server or workstation interventions. 

✅Reduced Compatibility Issues:

Web-based two-tier emulators are less vulnerable to OS changes, eliminating the need for extensive compatibility testing when upgrading operating systems like Windows.

✅Removal of Additional Software Dependencies:

Two-tier emulators eliminate the need for additional software like Java plugins or VPNs, reducing the maintenance overhead associated with these components.

✅Consolidated Maintenance:

All emulator-related tasks are concentrated on the mainframe, allowing maintenance teams to focus their efforts in one place rather than managing distributed systems.

✅Automatic Browser Updates:

Since the emulator runs in standard web browsers, it benefits from automatic browser updates handled by existing support groups and processes, further reducing maintenance efforts.

By streamlining maintenance and administrative processes, IT organizations can focus on more strategic initiatives rather than managing individual emulator installations.

 

3. Improved User Experience and Accessibility

Modern TN3270 emulators offer cross-platform compatibility, enhanced functionality, and an even better 3270 user experience than traditional TN3270 technology.  These improvements can lead to increased productivity and user satisfaction.

📌Improved Accessibility

▶️Browser-Based Access:

Web-based terminal emulators allow users to access 3270 applications through any standard web browser, eliminating the need for specialized client software.

▶️Device Independence:

Users can access mainframe applications from any web-enabled device, regardless of operating system or hardware, including mobile devices and tablets

▶️Screen Reader Compatibility:

Web-based solutions can provide a more modern, user-friendly interface while maintaining familiar 3270 ergonomics.

📌Improved Accessibility

▶️Modern Interface:

Web-based solutions can provide a more modern, user-friendly interface while maintaining familiar 3270 ergonomics.

▶️Customization and Automation:

Users can create shortcuts, automate repetitive tasks, and customize their experience to improve efficiency.

▶️Integration Capabilities:

Web-based emulators can integrate with other web applications and services, allowing for more seamless workflows.

By adopting web-based terminal emulators, organizations can provide a more accessible, user-friendly, and efficient experience for accessing mainframe applications while simplifying management and reducing costs.

4. Cost Reduction

Replacing legacy TN3270 emulators can result in significant cost savings for organizations.  And by transitioning to a more cost-effective solution, organizations can reallocate resources to other critical areas of IT infrastructure.

✅Elimination of Licensing Costs:

Some traditional emulators require expensive licensing, particularly those reliant on Java plugins.

✅Reduced Infrastructure Costs:

Web-based solutions often eliminate the need for middle-tier servers or other specialized hardware, reducing overall infrastructure expenses.

✅Lower Support Costs:

With simplified maintenance and fewer client-side issues, support costs can be substantially reduced.

✅Total Cost of Ownership (TCO) Reduction:

centralized web-based emulation can lead to up to 80% savings in TCO compared to traditional TN3270 emulators.

✅Possible VPN Cost Elimination/Reduction:

end-to-end encrypted HTTPS connections can potentially eliminate the need for a VPN, further reducing expenses.

✅Multi-Session Management Savings:

Web browsers' multi-tab capability can eliminate the need for a separate session manager.

 

✅BYOD Support:

By allowing users to access mainframe applications from any web-enabled device, organizations can reduce costs associated with providing and maintaining dedicated hardware.

 

5. Future-Proofing Your Mainframe Access

As technology continues to evolve, it's crucial to adopt solutions that can adapt to future organizational needs. Replacing TN3270 terminal emulators with pure web-based emulation significantly improves scalability, integration, and future innovation in several ways:

📌Improved Scalability

▶️Centralized Deployment:

Web-based emulators can be deployed centrally, eliminating the need for client-side installations and simplifying updates across the organization.

▶️Device Independence:

Users can access mainframe applications from any web-enabled device, regardless of operating system or hardware, supporting BYOD environments and flexible work arrangements.

▶️Load Balancing:

Web-based solutions can utilize load balancing architectures to ensure optimal resource allocation and maintain full functionality as user numbers grow.

📌Enhanced Integration

▶️Seamless application integration:

Web-based emulators can integrate 3270 screens into other web applications or workflows, enabling users to interact with mainframe data more intuitively.

▶️Single Sign-On (SSO): 

Many web-based solutions support SSO, allowing users to access multiple tools without repeated logins, improving convenience and reducing friction.

▶️API Connectivity: 

Web-based emulators can more easily connect with modern APIs, facilitating data exchange between legacy systems and contemporary applications.

📌Futur Innovation

✨Modernization Pathway:

Web-based terminal emulation serves as a stepping stone for organizations looking to modernize their legacy applications without immediate, risky overhauls.

✨Customization and Automation: 

Modern web-based emulators often include features like task automation and shortcut creation, streamlining workflows and improving operational efficiency.

✨Responsive Design: 

Web-based emulators can leverage responsive design principles, ensuring seamless functionality across various devices and screen sizes.

✨Integration with Emerging Technologies: : 

As web technologies evolve, web-based emulators can more readily incorporate new features and capabilities, such as AI-assisted interactions or advanced analytics.

By adopting web-based terminal emulation, organizations can significantly enhance their ability to scale operations, integrate legacy systems with modern applications, organizations can position themselves to better leverage their mainframe investments in the future.

Conclusion

The time has come for organizations to seriously consider replacing their traditional TN3270 terminal emulators. With enhanced security, simplified administration, improved user experience, cost savings, and future-ready capabilities, modern alternatives offer compelling advantages. By making this transition, companies can protect their critical mainframe assets while improving efficiency and user satisfaction.

Sebastian Dewar also talks about Transforming Mainframe User experience in the IBM Z Action Podcast.

You can get insights in this article: Transforming Mainframe User Experience– Insights from the IBM Z Action Podcast