Open-source software is software whose source code is publicly available for anyone to inspect, reuse, modify, and redistribute. Because the code is visible, developers and security teams can review how it works, identify bugs, and verify whether it includes unsafe behaviors or hidden dependencies.
In cyber security, open source is both a strength and a risk. Defenders use it for transparency, rapid patching, reproducible builds, and community-audited components. Attackers, however, may target open-source ecosystems by compromising maintainers, inserting malicious updates, abusing weak dependency controls, or publishing lookalike packages. Security teams often protect against these threats by pinning versions, verifying signatures, reviewing dependencies, and monitoring upstream changes. The key issue is not whether software is open or closed, but whether its code, releases, and update path can be trusted.