Episode 11 — Prevent unapproved execution with allowlisting logic and tightly governed exceptions
In this episode, we design secure configuration baselines so systems start secure by default and stay that way as they evolve. A baseline is not a wish list and it is not a one-time hardening sprint; it is the agreed starting point that every build should match unless there is a conscious, documented exception. When baselines are missing or vague, security becomes improvisation, and improvisation is how drift accumulates quietly until an incident proves the gap. A well-designed baseline reduces the number of unique decisions teams must make, because many security outcomes can be achieved through consistent defaults applied repeatedly. It also improves response speed, because when an incident occurs you can compare a system to baseline and immediately see what changed. The goal here is to build baselines that are measurable, repeatable, and realistic, so they can be enforced without constant exceptions and without breaking business operations. By the end, you should be able to define baseline goals, choose scope, select settings with rationale, and publish a baseline in a way that supports governance and continuous improvement.
Before we continue, a quick note: this audio course is a companion to our course companion books. The first book is about the exam and provides detailed information on how to pass it best. The second book is a Kindle-only eBook that contains 1,000 flashcards that can be used on your mobile device or Kindle. Check them both out at Cyber Author dot me, in the Bare Metal Study Guides Series.
Start by separating baseline goals into reducing attack surface and increasing resilience, because those two goals are related but not identical. Reducing attack surface is about removing or disabling what you do not need, such as unused services, unnecessary ports, risky defaults, and excessive privileges. When you remove exposure, you reduce the number of ways an attacker can gain initial access or escalate capabilities. Increasing resilience is about ensuring the system behaves predictably under stress, including through logging, monitoring, recovery readiness, and configuration integrity. Resilience often includes ensuring security controls start early, remain enabled, and report reliably, because detection and response depend on consistent telemetry. A baseline that only reduces attack surface can still fail if it is brittle, hard to maintain, or blind to changes. A baseline that only increases resilience can still fail if it leaves unnecessary exposure that does not need to exist. Keeping both goals visible helps you choose settings that balance prevention and recovery, which is what real environments require.
Next, define baseline scope across operating systems, applications, services, and security tooling, because baselines that focus on only one layer leave predictable gaps. Operating system scope includes account policies, authentication requirements, network service settings, local privilege boundaries, and basic hardening that applies broadly. Application scope includes configuration for common enterprise software such as browsers, productivity tools, remote access clients, and line-of-business applications where weak defaults can create direct exposure. Services scope includes what is enabled, what is disabled, how services run, and what network listeners exist, because services are often the most direct entry points for attackers. Security tooling scope includes Endpoint Detection and Response (E D R) agents, logging configurations, time synchronization, and other controls that make monitoring and response reliable. The scope must be aligned to what you can actually manage, because a baseline that includes unmanaged components will create constant noncompliance noise. You also need to decide how baselines apply to cloud workloads, where configuration is often expressed as templates and policies rather than as local settings. A baseline is strongest when it is explicit about what layers it covers and how those layers are validated.
To build real baseline skill, practice selecting settings with clear rationale and expected outcome, because settings without rationale become cargo cult security. Rationale answers why a setting exists in the baseline, such as preventing a known class of abuse, reducing privilege, or enabling reliable detection. Expected outcome answers what should change when the setting is applied, such as fewer exposed services, stronger authentication behavior, or more complete logs. This practice also forces you to consider operational impact, because a setting that improves security but breaks core workflows will drive exceptions or will be quietly undone. When you document rationale and expected outcome, you also create a tool for stakeholder conversations, because you can explain why a setting matters in plain language. Over time, this becomes a defense against baseline decay, because future teams can see the intent and are less likely to remove controls casually. The exam mindset here is that you are choosing defensible controls, not just collecting them. A baseline should represent deliberate decisions supported by risk logic and operational reality.
A quick win that prevents baseline paralysis is choosing a minimal baseline first, because a baseline that is too ambitious will never be enforced. Minimal does not mean weak; it means focusing on the highest leverage settings that reduce obvious exposure and establish essential telemetry. A minimal baseline might ensure strong authentication requirements, disable clearly unnecessary services, enforce basic network firewall rules, and ensure logging and endpoint protections are present and functioning. The value of starting minimal is that you can deploy and validate it quickly, learn where friction exists, and build trust with operations teams. Once the minimal baseline is stable, you can add controls in increments, which keeps exceptions manageable and avoids large disruptive shifts. This approach also aligns with continuous improvement, because each iteration can be measured and justified. Many programs fail by trying to define the perfect baseline before they have the governance and tooling to enforce it. Starting minimal is how you get to real enforcement sooner.
Baselines must also be measurable, which means they must be expressed as specific settings with acceptable values rather than as vague statements. Measurable settings include concrete parameters, such as whether a service is enabled, what authentication method is required, what cipher suites are permitted, or what logging level is configured. Acceptable values define what compliant looks like, including any allowable ranges or conditional rules that depend on role or environment. If you cannot measure a baseline, you cannot enforce it, and if you cannot enforce it, it becomes guidance rather than a control. Measurability also supports reporting, because you can quantify compliance and identify drift. It supports incident response, because you can confirm whether a system deviated from baseline before or after suspicious activity. Measurable baselines often require tooling integration, but the first step is simply making the baseline explicit enough that measurement is possible. The discipline is writing baselines like you intend to test them, because you do.
Baseline design also improves when you align baselines with roles such as workstation, server, kiosk, and administrator systems, because different roles have different acceptable risk and different operational needs. Workstations often need flexibility but still require strong identity controls, safe defaults, and protections against common user-driven attacks. Servers often need stability, predictable change, and reduced exposure, because they host services and often have privileged access paths. Kiosks often require lockdown, limited applications, and restricted user interaction, because their role is narrow and their exposure can be high. Administrator systems often need the strictest controls because they hold the keys to the kingdom, and compromise there is often catastrophic. Role alignment reduces exceptions because you are not forcing one baseline to serve incompatible needs. It also improves measurability because each role baseline can be tuned to predictable patterns of software and services. When role baselines exist, teams can classify systems and apply the right baseline automatically rather than debating settings system by system. This is how baselines scale.
Because baselines affect operations, mentally rehearse negotiating settings with operations and support teams, because negotiation is where baselines become real or get watered down into meaninglessness. A good negotiation posture is to start with outcomes, such as reducing exposure or improving detection, then discuss which settings achieve those outcomes with the least disruption. You also want to come prepared with evidence, such as what the current configuration state looks like, what incidents or findings the settings address, and what testing will be done to validate impact. Operations teams often worry about breakage, support load, and user frustration, and those concerns are legitimate because brittle baselines create unplanned work. Your job is to design baselines that are secure and supportable, and that often means phasing changes, using pilot groups, and creating rollback plans. Negotiation also benefits from clarity on exceptions, because some settings will be hard to apply universally, and a controlled exception path preserves baseline integrity. The goal is not to win an argument; it is to build a baseline that both security and operations can keep alive over time. Baselines that cannot be sustained are not baselines, they are temporary projects.
To keep the concept tight, create a memory anchor: baseline equals secure, stable starting point. Secure means the system begins with reduced exposure and essential protections enabled, rather than relying on later hardening that may never happen. Stable means the baseline is consistent, predictable, and maintainable, so it does not create constant support incidents or exception sprawl. Starting point means it is what you expect every build to match at creation time and throughout its lifecycle, not just during audits. This anchor also helps you respond when someone argues that baselines slow down the business, because you can reframe the baseline as the mechanism that reduces surprise work caused by insecure defaults. It also helps you resist the temptation to pack every possible security improvement into the baseline, because a baseline that is too heavy will not remain stable. The baseline should be the foundation, not the entire building.
Baselines also need versioning so changes stay traceable and reviewable, because baselines evolve as threats, technology, and business needs change. Versioning means you can identify what baseline version a system is intended to follow, what changed between versions, and who approved the changes. Traceability matters during incidents because you may need to understand whether a system was compliant with the baseline at the time of compromise and whether baseline changes introduced new behaviors. It also matters for governance because stakeholders will ask how baselines are reviewed, how changes are tested, and how exceptions are managed. A versioned baseline supports controlled rollout, because you can phase new versions across environments rather than changing everything at once. It also supports measurement, because you can track compliance against a specific baseline version rather than against a moving target. This is one of the simplest ways to make baselines feel professional and reliable, because it turns configuration guidance into a managed artifact. When versioning is in place, baseline changes become decisions, not accidents.
Now do a mini-review by restating three baseline principles from memory, because principles guide good decisions when specifics vary across platforms. One principle is measurability, meaning settings must be explicit and testable, with acceptable values defined. Another principle is realism, meaning the baseline must be supportable and aligned to role needs, so it can be enforced without constant exceptions. A third principle is outcome alignment, meaning settings must have clear rationale and expected impact tied to reducing attack surface or increasing resilience. You could also reinforce the principle of incremental improvement, where you start with a minimal baseline and add controls as you build operational confidence. These principles keep baseline design from turning into template copying or ideology. They also help you explain baseline choices to stakeholders, because you can justify why certain settings are included and why others are deferred. When you remember the principles, you can design and maintain baselines even as technology changes.
With those principles in mind, pick one baseline to publish and enforce, because progress happens when a baseline moves from draft to reality. Choose a baseline that has clear scope, stable ownership, and tooling support for measurement, such as a workstation baseline for a specific managed endpoint group or a server baseline for a controlled tier. Publishing means making the baseline accessible, documenting its version and rationale, and defining how compliance is measured and reported. Enforcing means setting expectations for rollout, creating a path for exceptions, and defining what happens when systems drift. The first published baseline does not need to be perfect, but it must be credible and maintainable, because its success will shape trust in the entire baseline program. Once it is enforced, you will gather real feedback about friction points, which is more valuable than hypothetical debate. Enforcement is the moment where baseline design becomes operational control. From there, you can refine, extend, and build a family of role-based baselines that cover the enterprise.
To conclude, designing secure configuration baselines means starting with clear goals of reducing attack surface and increasing resilience, then defining scope across operating systems, applications, services, and security tooling. It requires selecting settings with rationale and expected outcomes, avoiding blind template copying, and choosing a minimal baseline first so enforcement can begin quickly. Baselines must be measurable through specific settings and acceptable values, and they should be aligned to roles like workstation, server, kiosk, and administrator systems to reduce exceptions and support scale. Negotiation with operations matters because sustainment is the real test of a baseline, and the memory anchor baseline equals secure, stable starting point keeps the program grounded in practical outcomes. Versioning makes baselines traceable, reviewable, and governable as they evolve. Now schedule a stakeholder review, because baselines stay strong when changes are reviewed deliberately, tested carefully, and rolled out with shared ownership and predictable governance.
