Bob Delves into Advanced Linux Security Hardening with CIS Benchmarks

Bob’s next challenge was to implement advanced security hardening on AlmaLinux using the CIS (Center for Internet Security) Benchmarks. These benchmarks provide detailed recommendations to secure Linux systems against modern threats while maintaining usability.

“A hardened server is a fortress—time to make mine impenetrable!” Bob declared, diving into the CIS recommendations.

Chapter Outline: “Bob Delves into Advanced Linux Security Hardening with CIS Benchmarks”

1. Introduction: What Are CIS Benchmarks?

   • Overview of CIS benchmarks.
   • Why they matter for Linux security.

2. Installing Tools for Security Hardening

   • Setting up OpenSCAP and SCAP Security Guide (SSG).
   • Understanding the CIS AlmaLinux profile.

3. Applying CIS Benchmarks

   • Reviewing and implementing key CIS recommendations.
   • Automating compliance checks with OpenSCAP.

4. Customizing Hardening Policies

   • Editing security profiles for specific needs.
   • Managing exceptions and overrides.

5. Monitoring and Maintaining Compliance

   • Running periodic scans with OpenSCAP.
   • Keeping systems updated and secure.

6. Conclusion: Bob Reflects on Security Hardening Mastery

Part 1: Introduction: What Are CIS Benchmarks?

Bob learned that CIS Benchmarks are a set of best practices for securing IT systems. They cover a wide range of areas, including user management, file permissions, and network configurations.

Why Use CIS Benchmarks?

• Comprehensive: Covers every aspect of system security.
• Actionable: Provides step-by-step implementation guidelines.
• Standardized: Recognized by security experts and compliance frameworks.

“CIS Benchmarks are like a recipe for a secure server!” Bob said.

Part 2: Installing Tools for Security Hardening

Step 1: Installing OpenSCAP

• Install OpenSCAP, a tool for auditing and applying security baselines:

  sudo dnf install -y openscap-scanner scap-security-guide
  

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Step 2: Checking the Available Security Profiles

• List available security profiles for AlmaLinux:

  oscap info /usr/share/xml/scap/ssg/content/ssg-almalinux.xml
  

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Step 3: Selecting the CIS Profile

• Identify the CIS Level 1 profile:

  Title: CIS AlmaLinux 8 Level 1 - Server
  

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“The tools are ready—let’s harden this system!” Bob said.

Part 3: Applying CIS Benchmarks

Step 1: Running an Initial Scan

• Perform a compliance scan against the CIS profile:

  sudo oscap xccdf eval \
    --profile xccdf_org.ssgproject.content_profile_cis_server_l1 \
    --results results.xml \
    /usr/share/xml/scap/ssg/content/ssg-almalinux.xml
  

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• Review the results:

  sudo less results.xml
  

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Step 2: Addressing Key Recommendations

Bob focused on implementing high-priority fixes from the scan:

1. Disable Root Login via SSH:

   • Edit the SSH configuration file:

     sudo nano /etc/ssh/sshd_config
     

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   • Set:

     PermitRootLogin no
     

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   • Restart SSH:

     sudo systemctl restart sshd
     

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2. Set Password Aging Policies:

   • Configure aging rules in /etc/login.defs:

     PASS_MAX_DAYS 90
     PASS_MIN_DAYS 7
     PASS_WARN_AGE 14
     

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3. Restrict File Permissions:

   • Fix file permissions for critical directories:

     sudo chmod 700 /root
     sudo chmod 600 /etc/shadow
     

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4. Enable Firewall:

   • Start and enable firewalld:

     sudo systemctl enable firewalld --now
     

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5. Disable Unused Services:

   • List active services:

     sudo systemctl list-unit-files --type=service
     

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   • Disable unnecessary ones:

     sudo systemctl disable cups
     

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“Step by step, my server is becoming bulletproof!” Bob said.

Part 4: Customizing Hardening Policies

Step 1: Editing Security Profiles

Bob adjusted the security profile to meet specific business needs:

• Open the profile file:

  sudo nano /usr/share/xml/scap/ssg/content/ssg-almalinux.xml
  

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• Modify rules to fit requirements, e.g., relaxing password length for specific users.

Step 2: Managing Exceptions

• Use OpenSCAP to skip certain rules:

  sudo oscap xccdf eval \
    --profile xccdf_org.ssgproject.content_profile_cis_server_l1 \
    --skip-rule xccdf_org.ssgproject.content_rule_password_pam_minlen \
    --results results.xml \
    /usr/share/xml/scap/ssg/content/ssg-almalinux.xml
  

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“Customizing benchmarks ensures security doesn’t clash with usability!” Bob noted.

Part 5: Monitoring and Maintaining Compliance

Step 1: Automating Periodic Scans

Bob scheduled regular compliance scans:

• Create a cron job:

  crontab -e
  

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• Add the following:

  0 2 * * 0 sudo oscap xccdf eval \
  --profile xccdf_org.ssgproject.content_profile_cis_server_l1 \
  --results /home/bob/scap-results-$(date +\%Y\%m\%d).xml \
  /usr/share/xml/scap/ssg/content/ssg-almalinux.xml
  

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Step 2: Keeping Systems Updated

• Configure automatic updates:

  sudo dnf install -y dnf-automatic
  sudo systemctl enable dnf-automatic.timer --now
  

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“Regular audits and updates keep threats at bay!” Bob said.

Conclusion: Bob Reflects on Security Hardening Mastery

By implementing CIS benchmarks, customizing policies, and automating compliance checks, Bob achieved a robust security posture on his AlmaLinux server. He felt confident his system could withstand even sophisticated attacks.

Next, Bob plans to explore AlmaLinux for AI/ML Workloads to see how the platform performs with data-heavy applications.