No One’s Safe: Why Assume Breach Works

When the U.S. Department of Defense (DoD) admits that its networks may already be compromised, it’s a signal the rest of us can’t afford to ignore. The days of assuming the perimeter is safe are long gone. Instead, the only realistic way forward is to adopt an “assume breach” mindset, representing the idea that attackers are already inside your environment, and your job is to detect, limit, and contain them.

That’s the way the DoD is rethinking trust. For decades, organizations treated network access like a gated community: once you were in, you were trusted. But as breaches continue to escalate, that model looks more like leaving your front door wide open.

Today, security leaders are embracing the principle that trust must be continuously earned. Every device, every user, and every request needs to prove its legitimacy. Not just once at login, but throughout the entire session. The DoD’s shift underscores what many in cybersecurity have long argued: perimeter defenses alone aren’t enough, and static trust decisions can be exploited.

This is where the assume breach approach shines. By assuming an attacker already has access, teams design defenses that prioritize visibility, validation, and resilience. It’s a mindset that forces organizations to askif they really know the health and identity of every device connected to their systems.

The DoD’s acknowledgement isn’t just a policy shift; it’s validation that no organization, no matter how well-funded, is immune from compromise. For businesses, the lesson is straightforward: adopting “assume breach” isn’t a pessimistic view, it’s a pragmatic one. By treating compromise as inevitable, you build systems that are harder to exploit and faster to recover.

Vyas, Radhika. 2025. “The DoD Just Confirmed What We’ve Been Saying All Along: Trust Must Be Earned.” Secure W2.

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No One’s Safe: Why Assume Breach Works