Offensive cybersecurity is a complex and rapidly evolving field critical for protecting organizations and governments from cyber threats. However, due to its sensitive nature and potential ethical concerns, it is often shrouded in secrecy and controversy. This chapter comprehensively explains offensive cybersecurity, including its definition, capabilities, limitations, and legal and ethical implications. The chapter discusses the various offensive cyber operations that militaries and governments may use to defend themselves and deter potential attackers and the legal framework that governs such activities. It also explores the ethical considerations of offensive cybersecurity and the need for responsible use to avoid unintended consequences. Ultimately, the chapter seeks to promote a balanced understanding of offensive cybersecurity that acknowledges its potential benefits and risks and highlights the importance of using it judiciously and within legal and ethical boundaries.