Cybersecurity (or just security, as it’s called in tech and as we call it in this note) is no longer a niche responsibility managers can hand off—it’s become a core, strategic function in every company. Once business and communication moved almost entirely online, the stakes went way up. Now, with AI accelerating the pace of both attacks and defenses, the classic cat-and-mouse game of security engineers versus threat actors has turned into a high-speed chase. Today, security—like accounting or tax—is just one of those domains a well-rounded manager must understand, at least at a basic level. The goal of this note is to get you to that point. It explains what good security practices look like; introduces the fundamentals of the security stack, attack patterns, and defense patterns; and details how best to apply security to organizations, product teams and individuals, application components, data, and digital infrastructure.