Zero Trust Architecture

• Lateral movement is how breaches spread: once inside the perimeter, attackers roam until they find the crown jewels.
• Phished credentials convert to compromise unless access also requires device posture and context.
• Regulators and mature orgs now expect zero-trust-style controls: MFA everywhere, least privilege, microsegmentation.

A castle trusts everyone past the moat; an embassy re-checks credentials, escort, and purpose at every door.

• Every request is evaluated against identity, device health, location, data sensitivity, and risk before access is granted.
• mTLS and short-lived credentials replace 'inside the network' as the trust signal for machine-to-machine calls.
• Microsegmentation shrinks blast radius: workloads can only reach the specific peers their job requires.
• Continuous evaluation rescinds access on risk change: a device gone rogue loses its session, not just its next login.

• An org replaces a huge VPN with identity-aware access: users get app-by-app sessions brokered by their IdP.
• A microservice platform issues mTLS certificates per workload so pod A can only talk to pod B.
• A hybrid team adds device-posture checks: a non-compliant laptop is denied even with valid credentials.

• Start with identity: single source of truth for users and work-relative attributes.
• Scope access by 'what the role needs today' and expire it aggressively.
• Instrument every allow/deny decision for continuous tuning and incident forensics.
• Treat device posture as a signal, not a binary: combine it with context and behavior.

• Labeling a 'modern VPN' as zero trust because it does single sign-on.
• Replacing the perimeter with an unmanaged cloud: zero trust without visibility is theater.
• Tolerating standing admin credentials that skip the same verification everyone else must pass.
• Microsegmenting so thinly that the policy graph becomes impossible to operate and maintain.

• When an access path is denied unexpectedly, check the deny reason: identity, device, or context policy.
• Trail mTLS failures through cert validity first: clock skew and CN/SAN mismatch cause most hard failures.
• Evaluate policy as a pipeline: which signal flipped in the last deny? Log every factor, not just the verdict.

• Zero trust centralizes trust in the identity provider and policy engine — protect those like the crown jewels.
• Management planes (certificate issuers, policy engines) need strong isolation and MFA with rare exceptions.
• Document exemptions; a zero-trust org with silent exceptions has reverted to perimeter trust.