A Practical Guide to Applying CIS Benchmarks for System Hardening

Introduction

In today’s world, where cyber threats keep evolving every day, system security is no longer optional – it’s a must. Many organizations depend on trusted frameworks to secure their infrastructure. One such framework is the CIS Benchmark, created by the Center for Internet Security (CIS).

CIS Benchmarks are detailed recommendations that help you configure operating systems, servers, databases, and applications securely. Whether you’re managing a Linux server or a Windows workstation, these benchmarks give you a clear checklist of what to configure and why it matters.

This blog explains what CIS Benchmarks are, why they’re important, when you should use them, and how they can improve your system security  with some real examples from implementation experience.

What Are CIS Benchmarks?

The CIS Benchmarks are a set of recommended practices for system configuration security. They are created by industry experts, government specialists, and cybersecurity professionals who collaborate to specify what “secure configuration” for each platform should entail.

A list of security controls, such as turning off unused services, establishing appropriate file permissions, or enforcing password policies, is provided by each CIS Benchmark. The purpose of these controls is to lower risk without impairing regular operation.

The benchmarks are divided into two levels:

  • Level 1: Concentrates on fundamental security configurations that don’t impact system functionality. Perfect for the majority of organisations.
  • Level 2: For sensitive or high-security environments, more stringent security configurations are added.

In short, CIS Benchmarks give you a step-by-step guide to make your systems more resilient against attacks, serving as a vital foundation for effective database security & compliance consulting.

Why CIS Benchmarks Are Important

Misconfigurations, rather than new vulnerabilities, are the cause of many security incidents. Attackers can gain access by making a simple error, such as leaving /tmp executable or permitting unfettered SSH access. By providing validated settings that have been tested in a variety of environments, CIS Benchmarks aid in avoiding such errors.

Following CIS Benchmarks also helps organizations:

  • Stay compliant with standards such as ISO 27001, NIST, and SOC 2
  • Reduce the time and cost needed for audits
  • Create consistency across systems and environments
  • Build a strong security foundation from day one

In short, implementing CIS Benchmarks means your systems are not only secure , they’re also auditable and standardized, which is vital for long-term security management.

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Key Benefits of Using CIS Benchmarks

  1. Improved Security Posture:
    Each CIS Benchmark control addresses a particular security vulnerability. By implementing them, you shut down numerous typical attack vectors.
  2. Consistency Across Systems:
    With all your systems having the same configuration settings, it becomes simpler to handle and audit them.
  3. Ease of Validation:
    Automated testing of your systems against CIS Benchmark rules using tools such as CIS-CAT, OpenSCAP, or Lynis spares you effort.
  4. Community-Driven and Trusted:
    CIS Benchmarks are constructed by a worldwide group of experts, so they adapt to emerging threats and technology.
  5. Vendor Neutral:
    Regardless of whether you’re using Linux, Windows, AWS, or GCP, there’s a benchmark for nearly every top-tier platform.

When Should You Use CIS Benchmarks?

CIS Benchmarks can be applied at different stages depending on your setup:

  • During Initial System Setup: Prior to installing a server, set it up according to the benchmark. This avoids unsafe defaults.
  • During Regular Maintenance: Review systems periodically to ensure no configuration drift has occurred.
  • Before Audits or Compliance Checks: CIS alignment helps prepare for security audits.
  • In CI/CD Pipelines: Automate security checks as part of compliance workflow for ongoing compliance.

In short, CIS Benchmarks aren’t just for audits – they’re for everyday secure operations.

Real-World Examples of CIS Benchmark Implementation

To understand how CIS Benchmarks strengthen system security, let’s look at two practical examples – securing the /tmp directory and enforcing authentication for single user mode.

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Example 1: Securing /tmp with nodev, nosuid, and noexec

The /tmp directory is used for temporary file storage by users and applications. Because it’s world-writable, it can be exploited if not properly configured.
CIS recommends that /tmp should be mounted on a separate partition with the nodev, nosuid, and noexec options to prevent misuse.

Audit

To verify the mount options for /tmp:

findmnt -nk /tmp

Expected output example:

/tmp   tmpfs  tmpfs  rw,nosuid,nodev,noexec

To check each option individually, you can run:

findmnt -kn /tmp | grep -v nodev     # Verify nodev
findmnt -kn /tmp | grep -v nosuid    # Verify nosuid
findmnt -kn /tmp | grep -v noexec    # Verify noexec

If nothing is returned, the respective option is correctly applied.

  • nodev ensures that no special device files (block or character devices) can be created inside /tmp.
  • nosuid prevents executable files in /tmp from running with elevated privileges, blocking privilege escalation attacks.
  • noexec stops execution of programs from /tmp, preventing attackers from running malicious scripts from this directory.

Mounting /tmp separately with these options reduces attack surfaces and helps maintain system stability and integrity.

Solution using Ansible:

This configuration can be applied automatically using an Ansible role. The role mounts /tmp as a separate partition with secure options (nodev, nosuid, and noexec) in line with CIS recommendations.

Using automation ensures that these security controls are consistently enforced across all managed nodes, reducing manual effort and configuration drift.

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Example 2: Enforcing Authentication in Single User and Emergency Modes

Single user and emergency modes are recovery states that provide direct root access to troubleshoot or repair the system.
If authentication isn’t enforced, anyone with physical or console access could use these modes to gain root privileges without a password.

CIS recommends using sulogin to ensure authentication is required in both modes.

Audit

To check if authentication is enforced, run:

grep /sbin/sulogin /usr/lib/systemd/system/rescue.service
grep /sbin/sulogin /usr/lib/systemd/system/emergency.service

Expected output example:

ExecStart=-/bin/sh -c "/sbin/sulogin; /usr/bin/systemctl --fail --no-block default"

If /sbin/sulogin appears in both outputs, it confirms that authentication is properly enabled.
This setup ensures that only authorized administrators can access recovery modes, preventing unauthorized users from bypassing normal login security.

Solution with Ansible

The same configuration can be enforced automatically using Ansible.
The following task updates both rescue.service and emergency.service files to include sulogin, ensuring that authentication is always required when entering single user or emergency mode.

Using this automated approach ensures all systems consistently enforce authentication in recovery modes, reducing the risk of unauthorized access.

Conclusion

CIS Benchmarks offer a dependable and workable approach to hardening systems against prevalent misconfigurations. The guidelines enable administrators to normalize settings, enhance defenses, and ensure compliance with established security standards. Whether implemented manually or using automated tools such as Ansible, CIS Benchmarks enable the creation of a uniform and secure environment that’s simpler to manage and audit

Frequently Asked Questions (FAQs)

1. Who creates CIS Benchmarks?

They are authored by the Center for Internet Security (CIS) with contribution from cybersecurity professionals, vendors, and government agencies.

2. Are CIS Benchmarks equivalent to DISA STIGs?

No. CIS Benchmarks are best practices developed by the community, whereas STIGs are U.S. Department of Defense security guides.

3. Can CIS Benchmarks be automated?

Yes. CIS-CAT, OpenSCAP, and Ansible roles can automatically scan and apply CIS configurations.

4. In what ways do CIS Benchmarks assist with compliance?

They closely align with standards such as ISO 27001, NIST, and SOC 2, which enable organizations to pass audit and security compliance requirements.

5. Do CIS Benchmarks have any impact on system performance?

Level 1 settings do not have much or any effect. Level 2 might slightly impact it, as they contain more strict security rules.

6. Are CIS Benchmarks customizable?

Yes, you can make them fit your company’s requirements , if changes are documented and approved.

References

  1. Center for Internet Security (CIS) Benchmarks
    Official documentation and benchmark guides for different operating systems and platforms.
    🔗 https://www.cisecurity.org/cis-benchmarks
  2. CIS-CAT Pro Assessor User Guide — Center for Internet Security
    Details on using CIS’s official auditing tool to assess compliance.
    🔗 https://www.cisecurity.org/tools/cis-cat-pro
  3. OpenSCAP Project Documentation
    Open-source framework for automated compliance checking and vulnerability assessment.
    🔗 https://www.open-scap.org/

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