The code we inherit – hidden security risks in old systems

Many organizations are working intensively on digitalization and new developments. New solutions, modern frameworks and cloud platforms are often in focus. At the same time, older systems continue to live on in the background. They often carry mission-critical functions, but rarely receive the same attention. From a cybersecurity perspective, this may be where the greatest risks lie.

Technical debt as a security risk

Building on existing code is common. Many systems have evolved over several years with different developers, tools, and requirements. The result is often a complex environment that is difficult to monitor and maintain, which also affects security.

Old components and dependencies are not always updated and may contain known vulnerabilities. Code written in another era often lacks modern security principles. Accountability can be unclear, especially in systems that many people have worked with over the years. Older integrations can create unexpected attack surfaces. And when the focus is on new development, the old easily falls into the shadows.

Thinking “it still works” is human, but that’s precisely why old systems can become the weakest link in an organization’s security.

Therefore, we must secure the old

Security work is not just about new projects and technologies. Older systems are often a central part of the business, and a vulnerability there can have major consequences. An outdated API, a forgotten server, or a library that hasn’t been updated in years can open up avenues that no one is monitoring anymore.

Taking responsibility for cybersecurity therefore also means taking care of what we have already built.

How development teams can act

There are several ways to reduce risks in legacy systems:

• Map dependencies and versions to understand what is actually being used.
• Perform security audits even on legacy code. Automated analysis and penetration testing often reveal more than you think.
• Plan for refactoring where needed. Security is a strong argument for modernization.
• Strengthen protection around legacy systems through better access controls, logging, and monitoring.
• Invest in skills development. Awareness and knowledge are often the most effective protection.

A cultural issue as much as a technical one

Security is not just about code, it’s about culture and priorities. If older systems are seen as something to “be replaced later,” they risk being left out of security efforts. But if we instead view them as an active part of our security environment, it’s natural that they will be subject to the same demands for quality, follow-up, and improvement as new solutions.

Old systems are not just a cost. They are part of the organization’s digital backbone – and therefore also part of its security.

Summary

Cybersecurity is about integrity and long-term thinking. New systems should be built secure, but what we already have must be managed with the same care. Legacy environments will rarely disappear overnight, but risks can be reduced with the right strategy, the right skills and a culture that takes security seriously.