FOSS stands for Free and Open Source Software. It refers to software that is both free to use and whose source code is openly available for anyone to view, modify, and distribute. In cybersecurity, FOSS tools are widely used because their transparency allows experts to inspect for vulnerabilities, customize features, and ensure there are no hidden backdoors. The open nature of FOSS encourages community collaboration, leading to rapid identification and patching of security flaws. However, users must also be vigilant, as open code can be examined by malicious actors as well. FOSS is a cornerstone in building secure, flexible, and cost-effective cybersecurity solutions.