System Hardening Explained: Types, Techniques, Examples & Mistakes to Know

The broad umbrella of today's IT security includes standards, tools, technologies, and human practices that reduce risk and protect your systems. System hardening is one conceptual catch-all for those components of IT security — but what does system hardening mean in relation to your actual day-to-day operations? And how do you achieve system hardening without burdening your whole team?

In this blog, we’ll cover common questions about system hardening, explain the types of system hardening often used in IT security, share system hardening examples, define the relationship between compliance and hardening, and highlight how infrastructure as code can automate system hardening across your infrastructure. 

What Does System Hardening Mean?

In cybersecurity, system hardening means using tools to secure technologies in an IT system. System hardening includes securing system elements against vulnerabilities and attacks, including servers, networks, apps, databases, and more.

What Makes System Hardening Important?

System hardening is an important process because it minimizes the attack surfaces of a system, which are often exploited by cyber criminals. The purpose of system hardening is to remediate vulnerabilities before they can be exploited by threat actors, or before they cause business interruptions like an unplanned outage.

For evidence of the importance of system hardening, just look at these recent trends in DevSecOps automation:

• AI is enhancing threat detection and response, but it’s also being exploited by attackers to automate sophisticated attacks. System hardening is one of the most reliable means of counteracting AI-driven threats to system security.
• Supply chain security is getting a lot more attention today than ever before. System hardening helps secure and support your own systems, which is great for preventing vulnerabilities and threats from taking you down — but it also helps you establish trust and enforce secure configurations and versions for the third-party software you use (and dependencies built into them). 

System Hardening Examples, from Server & OS Hardening to Physical Measures

System hardening isn’t just one thing; it’s a comprehensive measurement of your system’s security. Different technologies require different tactics for hardening.

As such, the system hardening examples shown below have their own nuances and checklists. They're all enacted and measured differently, so they should be evaluated against applicable best practices and mitigated as part of an overall risk management program.

Also, great system security doesn't get done by just one department. Watch a webinar or download an eBook about getting IT, compliance, and security teams on the same page.

SECURITY WEBINAR    SECURITY EBOOK

Some system hardening examples include:

The Differences Between System Hardening, Server Hardening, App Hardening & More

All kinds of system hardening are important to maintaining a strong security posture across your infrastructure. A modern network comprises many heterogenous devices and disparate technologies. On top of that, those devices and technologies are managed across a variety of on-premises, private cloud, and public cloud environments. It is reasonable to expect good security hygiene regardless of the type and physical location of the software, firmware, or hardware. 

But system hardening activities, while conceptually similar, will differ based on the type, role, or location of the asset. The requirements for an end user’s workstation in an office center are going to be quite different than those of a web server operating in the DMZ, for example. Likewise, firewalls and routers will each have their own requirements.

Zero Trust is Another Big Part of System Hardening

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Multiple hardening layers may exist within even a single asset. For example, once a server has been hardened at the OS and firmware level, its applications may then need to be hardened by installing a specific version from only trusted application repositories. Rules will need to be established and managed for each layer of a system.

Prioritizing and then systematically hardening each of these elements makes systems more secure. In turn, that reduces the risk of a hacker accessing restricted resources, or the accidental or malicious disruption of critical business services. 

Steps for System Hardening & Tips You Can Use

Download a Free System Hardening Checklist Go further with the decision maker's guide, including specific system hardening tools and tactics to secure systems at every layer. Download the Guide

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A system hardening checklist refers to a list of practices and action steps you can take to ensure system hardening. Here are a few common items you’ll find on a system hardening checklist (be sure to grab our comprehensive system hardening checklist for specific to-dos): 

• Apply patches for known vulnerabilities. Do it in a timely manner — as long as it's been tested, don't wait to patch software!
• Require strong passwords and MFA. Security automation tools can help implement robust password policies and prevent unauthorized system access.
• Limit user privileges. Use zero trust and the principle of least privilege to grant access to just the users who need it — then use role-based access control (RBAC) to limit access by their role and function in the organization.
• Alter unsecure default settings with configuration management or even policy as code (PaC).
• Disable unnecessary services. Tools like Windows Services Manager and SCCM can help.
• Whitelist critical applications. Try Windows Defender, macOS Gatekeeper, Carbon Black, SELinux — or, for scale, use a configuration management tool.
• Remove or disable unnecessary system applications. Package managers and configuration management tools make it a lot easier to prevent unnecessary system applications from compromising system security (instead of making you manually disable each app).
• Remove or disable superfluous drivers. A configuration management system can do this for large IT, but for smaller setups, you can also try custom automation scripts or even use the built-in tools that come with your chosen OS (like Windows Device Manager or Linux command line).
• Maintain supported OS versions. A patch management tool or a configuration management system is practically a necessity for environments running multiple OSes.
• Establish appropriate firewall rules with built-in tools like Windows Firewall, SIEM tools, or configuration management tools like Puppet, Ansible, and Chef.

In reality, system hardening is bigger than a single checklist. But these common items can give you a point from which to work toward hardening your systems. Expect to implement security-centric technologies, such as multi-factor authentication (MFA), privileged user vaulting, and encryption. System hardening requirements often includes establishing a cadence of security activities, including penetration testing and audits.

The Three Most Common Mistakes in System Hardening

Mistake #1: Ignoring patches and updates.

Skipping important updates, not properly testing patches, and having a generally chaotic patch management process are great ways to increase the risk of a security incident in your systems. And the increase of vulnerable code and new tools for attacking systems means patching is more important now ever.

Mistake #2: Failing to test system hardening measures before locking them in.

There is such a thing as over-hardening! The secret to system hardening is to find the measures that keep your systems secure without restricting operational needs. Be sure to test any changes to your system hardening in a controlled environment before making them the new standard. Otherwise, you’re looking at downtime and potentially weaker security because misconfigurations might go unnoticed.

Mistake #3: Setting it and forgetting it.

System hardening isn’t one-and-done. Configuration drift can easily throw systems from a secure, hardened state into a vulnerable, non-compliant posture without your team ever even noticing. That's why regular configuration monitoring is extremely important for keeping systems hardened over time — not just getting the green check mark and calling it done. 

Does System Hardening Fall on the Security Team or On the Operations Team?

Typically, security teams handle many aspects of system hardening. But IT operations can be instrumental in an effective, minimally invasive system hardening approach. The real answer is that both security and operations teams have important roles to play in making sure systems remain configured to a secure standard.

IT operations departments take the lead when it comes to the initial configuration and rollout of technology. If security standards have already been established, then these kinds of system hardening requirements can be incorporated into the build and deployment processes. But what happens when the security configuration is not part of the initial process, or when a change is subsequently made to either the asset or to the baseline? 

Security teams define and then uphold security standards. However, the frequency with which the security team performs scans may be inconsistent with ops's desire for continuous compliance. Giving ops the ability to swiftly make minor course adjustments with automation — without giving them more work to do or a whole bunch of new tools to learn — can help you achieve continuous compliance and system hardening rather than waiting for the next audit. 

Combining the talents of operations and security teams provides an optimal balance. Security staff define and oversee compliance, while operations evaluates current state and realigns configurations along the way. 

How Do You Measure System Hardening?

Compliance regulations often demand a recurring assessment of how well your systems adhere to a desired state. They also require that you show proof of that adherence as part of self-certification or to satisfy a formal audit. Organizations lacking any formal directives should establish a comprehensive internal security policy to guide their activities. 

Hardening is accomplished by first establishing the baseline configuration, which is a declaration of the hardened state of the system. Experts encourage the use of security standards as they provide prescriptive guidance and expert input from cybersecurity specialists. Systems should be initially aligned with the pertinent baseline, and then monitored frequently to expose deviations from a hardened state. Deviations must be addressed quickly to minimize the risk of a vulnerability being exploited.    

IT operations teams may experience compliance scans as part of a formal (and often infrequent) audit activity by a different team or department — often relying on expensive external resources. This approach is prone to fire drills and unexpected spikes in remediation activity any time non-compliance is discovered, potentially long after the drift initially occurred.

While formal audits and security scans are beneficial for validating the effectiveness of hardening policies, compliance verification should happen with far greater frequency to reduce the impact on staff while minimizing the risk profile.

How Does Compliance Help Harden Your System?

Compliance can act like a handbook for system hardening. Hardening systems according to compliance standards saves time for DevOps teams because they don’t have to start from scratch, and it makes audits easier by making sure system hardening measures already align to commonly accepted standards.

Standards, frameworks, and benchmarks for compliance describe security requirements for a system, and some frameworks even include instructions for configuring those security measures.

•  Q: Why does continuous compliance matter, anyway?
• A: Because your attack surfaces aren’t getting smaller — and neither is the cost of a failed audit.

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CIS Benchmarks, DISA STIGs, NIST, CMMC, and more standardize the risk evaluation and mitigation process to make your team more efficient at system hardening. Rather than reinventing the wheel for each new CVE, you can use a compliance framework to craft your security configurations once (like a rulebook) and then use automation and configuration management to enforce them continuously.

Still, you can be compliant without being secure. Learn more about the complex relationship between security and compliance >> 

Compliance frameworks and security standards typically provide guidance on system hardening and standardizes the risk evaluation and mitigation process. It also reduces duplication of effort by letting you craft, adhere to, and continually refine a set of rules rather than reinventing the wheel for each new common vulnerability and exposure (CVE).

How Automation Makes System Hardening Easier (Even at Scale)

System hardening is a complex and resource-intensive activity. It also requires specialized security skills. Multiply this effort by the large number of IT assets that most organizations are managing, along with the frequency with which they should be reassessed, and it doesn’t take long to determine that automation is the only way to achieve success.

Inventorying Assets

Think about managing inventory in a modern supermarket. Dozens of aisles, hundreds of shelves, and thousands of items must all be verified for adherence with an item’s expected location, accurate pricing, and expiration date.

Supermarkets calculate stock on hand based on purchases that pass through the checkout, combined with an occasional overnight audit usually performed by temporary staff. But how often have you visited a store and seen eggs discarded and spoiling in the cereal aisle? Or found out that the inventory in-store or sale price didn’t match what was in their computer? 

Doing it all manually would take weeks, and the review would be long out of date before you're done. Now think about doing that messy inventory analysis regularly. It’s the same with taking inventory of technology assets. It takes constant care to ensure that... 

• Only authorized applications are installed
• Configuration settings are appropriate
• Operating systems are supported and patched
• Critical firewalls have the correct rules applied

As you can imagine, that's practically impossible to ensure without some degree of automation. 

Automation eliminates the error-prone and time-consuming effort of performing even a cursory inventory. You may not be able fully to automate system hardening (again, system hardening is a qualitative measurement, not a product or service), but with deep visibility, you can perform in-depth analysis of every aspect of configuration across your system faster and with less human input.

Configuration Drift Detection & Remediation

Instead of discovering configuration drift once a year during an audit, you can detect that drift — which could’ve just popped up or it could’ve been sitting there for months — within minutes. Issues can even be corrected automatically. In that way, automation helps you achieve hardening of the various components of your system. Then, you can enforce continuous compliance with those vital benchmarks and frameworks, all with automation as the backbone.

24/7 Enforcement of System Hardening Measures

Agent-based automation reinforces system hardening by continuously monitoring and enforcing the desired state of systems across your infrastructure. With agents deployed directly on managed nodes, it can provide real-time feedback and remediation capabilities, giving agents a significant leg up in the case for agent-based vs. agentless automation for security.

When configurations drift from their hardened state, the agent detects the change and automatically corrects it, ensuring systems remain aligned with security and compliance benchmarks. This approach not only eliminates the manual burden of constant monitoring but also reduces the risk of vulnerabilities caused by misconfigurations or oversights. By maintaining secure, consistent configurations, agent-based automation safeguards critical assets while streamlining the operational processes that support system hardening.

The Puppet Enterprise platform is the leading solution for deploying secure infrastructure, configuring a desired state, and managing infrastructure with confidence at scale. Puppet unearths drift and other vulnerabilities using an integrated edition of the official CIS configuration assessment tool (the CIS-CAT® Pro Assessor). And with Security Compliance Enforcement (available in Puppet Core and Puppet Enterprise Advanced), you can automatically enforce system hardening configurations keep your systems in alignment with CIS Benchmarks and DISA STIGs automatically.

Get a demo of Puppet automation for hardening or download our free decision maker's guide and checklist for system hardening now.

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