The University of Sydney has disclosed a data breach involving unauthorized access to an internal code library that contained historical data files. Approximately 27,500 individuals were affected, including current and former staff, students, alumni, and a small number of supporters. While the exposed data was not part of active systems, the incident underscores how legacy datasets embedded in development environments can create long-term security risks if not properly governed.

Universities manage vast and complex digital environments that span decades of research, teaching, and administrative operations. Code repositories, often used for development and testing, can accumulate legacy data over time. When such repositories are insufficiently secured or reviewed, they can become attractive targets for attackers seeking personal information that may no longer be actively monitored.

According to the university, attackers accessed and downloaded data from an online code storage and development library. The repository included historical data files that were likely used for testing when the code was originally developed.

The compromised files contained personal information of staff employed in September 2018, as well as records associated with alumni, students, and affiliates dating back as far as 2010.

The university stated that there is currently no evidence that the stolen data has been published or misused.

The affected platform was a single code library used for software development purposes. Within that repository were embedded datasets containing real personal information, rather than anonymized or synthetic test data.

These files included names, addresses, phone numbers, dates of birth, and basic employment details. Although the repository was not part of the university’s core production systems, it was accessible online and ultimately exposed to unauthorized access.

Importantly, the university emphasized that no other systems were affected, and the breach was limited to this specific development environment.

In total, approximately 27,500 individuals were impacted:

While the data is described as historical, the types of information involved could still be valuable for phishing, identity theft, or social engineering if misused.

This incident highlights a recurring issue across many organizations: legacy data persisting in places not designed for long-term storage of personal information. Development and testing environments are often treated as lower risk, yet they can contain sensitive data that remains exposed for years.

For large institutions, especially in education and research, this serves as a reminder that data minimization and regular audits must extend beyond production systems.

Security teams frequently focus on protecting live databases while overlooking older repositories and test environments. This breach reinforces the need for strict controls on what data is allowed in code libraries, along with routine reviews to remove or sanitize historical datasets.

The university’s prompt disclosure and coordination with authorities align with best practices, but prevention remains the more effective strategy.