Cyber Incident

Common Vulnerabilities in Legacy Systems and How to Mitigate Them

Sourjesh Mukherjee
May 15, 2024

Legacy systems are the workhorses of many businesses, the dependable but aging software and hardware applications that keep core operations running. Imagine them as the trusty family car with hundreds of thousands of miles on the odometer. It still gets you where you need to go, but it lacks the safety features, fuel efficiency, and performance of newer models.

These outdated software applications, databases, and codebases, while once reliable workhorses, struggle to keep pace with the digital trend.

Examples of legacy systems include:

  • Old Enterprise Resource Planning (ERP) systems: These were often built with a monolithic architecture, making them inflexible and difficult to integrate with newer technologies.
  • Outdated databases: Hierarchical and older relational database systems may lack the features and security needed for modern applications.
  • Custom code: Businesses may still rely on proprietary software written in languages like COBOL, posing challenges for maintenance and updates.

What is the Problem with Legacy Systems?

While legacy systems may seem harmless, they harbor significant vulnerabilities that can leave your business exposed. 

Here's why legacy systems can be a security nightmare:

  • Outdated Security Measures: Legacy systems were built at a time when cyber threats were less sophisticated. They often lack the firewalls, encryption protocols, and multi-factor authentication needed to keep hackers at bay. A study by Accenture found that 85% of IT leaders in government agencies believe not updating legacy systems threatens their future.
  • Compatibility Issues: Modern security solutions might not be compatible with legacy systems, hindering real-time monitoring and response to security incidents.
  • Unpatched Vulnerabilities: As software vendors prioritize updates for their newer products, legacy systems become vulnerable to known exploits readily available to attackers. The FedEx breach in 2018 is a prime example. An Amazon S3 server, likely a legacy system from a previous acquisition, was left unsecured on FedEx's.

Here's how recent events showcase the dangers of legacy systems:

  • FedEx Breach: An Amazon S3 server, likely a forgotten legacy system from a previous acquisition, was left unsecured on FedEx's network, exposing sensitive data.
  • Grand Traverse County (Michigan): Relying on decades-old "spaghetti code" in its mainframe environment created security vulnerabilities and hindered modernization efforts. 

Legacy software is a big issue! A study found that major tech companies like Microsoft and IBM have tons of older products still in use by businesses, followed by Micro Focus, BMC, and Oracle. This is because many companies have been around for a long time and haven't gotten around to updating their software. This can be risky because these older programs may not have the latest security features.

Mitigating Risks in Legacy Systems: A Multi-Pronged Approach with Real-World Examples

Replacing them entirely is ideal, but the high costs and disruption involved often make it a last resort. Fortunately, businesses can leverage a multi-pronged approach to significantly mitigate security risks and extend the lifespan of these critical systems.

1. Security Audits and Assessments: Shining a Light on Vulnerabilities

Take the example of Grand Traverse County, Michigan. Their reliance on decades-old "spaghetti code" within their mainframe environment went undetected for years. A thorough security audit would have revealed these vulnerabilities, allowing the county to take corrective action before a potential breach.

Regular security assessments should be conducted by qualified professionals who can examine configurations, patch management processes, access controls, and security logs. Think of these logs as a system's diary, recording access attempts, suspicious activity, and security events. Analyzing these logs can reveal patterns and potential weaknesses that need to be addressed.

2. Patch Management: Plugging the Holes Before Attackers Do

Legacy systems are often missing the crucial security updates that patch known vulnerabilities.

Prioritizing and applying security patches as soon as they become available is critical. While some vendors may no longer support older software versions, working with specialists who maintain expertise in legacy systems can help bridge this gap.

3. Access Controls: Granting Access Only to Those Who Deserve It

Implementing role-based access controls (RBAC) ensures that only authorized users have access to specific data and system functions based on their job requirements. Think of it like issuing personalized keys to different sections of your security system.

Multi-factor authentication (MFA) adds an extra layer of security by requiring a second verification step beyond a simple username and password. This additional hurdle significantly reduces the risk of unauthorized access, even if a hacker steals login credentials.

4. Network Segmentation: Building Firewalls Within Firewalls

Network segmentation involves creating isolated network zones for different systems or departments. This way, if a legacy system gets breached, the damage is contained within its designated segment, preventing attackers from easily pivoting to access other parts of the network.

Network segmentation creates isolated zones within the larger network infrastructure. Legacy systems, with their inherent vulnerabilities, can be placed within their own "district" to minimize the potential impact of a breach.

5. Data Encryption: Safeguarding the Crown Jewels

Businesses should encrypt sensitive data stored within legacy systems. Data encryption scrambles information using a key, making it unreadable to anyone who doesn't possess the decryption key.

In the aftermath of the Equifax breach in 2017, millions of customer records were compromised because they were stored in plain text on a legacy system. Had the data been encrypted, even if attackers gained access, the information would have been useless without the decryption key.

6. Incident Response Planning: Rehearsing the Play Before Game Day

Being prepared for a security incident is crucial, especially when dealing with legacy systems. An incident response plan outlines roles, responsibilities, communication protocols, and containment procedures to be followed in the event of a breach. Regularly testing and updating this plan ensures a coordinated and efficient response that minimizes downtime and damage.

Think of an incident response plan as a fire drill for your IT infrastructure. Just as practicing fire drills prepares everyone for an emergency, a well-rehearsed incident response plan ensures everyone knows their role and how to respond effectively in the case of a security breach.

7. Modernization Roadmap: A Gradual Shift Towards a Secure Future

While the strategies above help mitigate risks, a long-term modernization plan is essential. This could involve migrating to cloud-based solutions that offer enhanced security features and easier scalability. Alternatively, a phased upgrade approach can involve replacing specific components of the legacy system over time, prioritizing the most critical functionalities first.

By implementing these strategies, businesses can significantly reduce the security risks associated with legacy systems. Remember, legacy systems are not going away anytime soon. However, by taking a proactive approach to security, businesses can ensure they remain operational and protected in the digital age.


Legacy systems, while posing security challenges, can be secured through a multi-pronged approach. Regular security audits, vigilant patch management, and robust access controls form the foundation for a strong defense. Network segmentation and data encryption add extra layers of protection, while an incident response plan ensures a swift and coordinated response to security breaches. Finally, a modernization roadmap paves the way for a more secure and sustainable IT infrastructure in the long run. By employing these strategies, businesses can mitigate risks and ensure their legacy systems continue to operate securely and efficiently.

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