System Hardening Checklist Covers Access, Network, Logging, and Platform Controls
Summary
A practical guide to reducing attack surface through system hardening, covering access controls, network and firewall settings, patching, Windows and Linux configurations, logging, physical security, and ongoing audits.
Key points
- Disable default and inactive accounts, enforce MFA for privileged access, and apply least privilege.
- Use default-deny firewall rules, close unused ports and services, and segment networks to limit lateral movement.
- Maintain a patch cadence, inventory installed software, and replace or isolate end-of-life systems.
- Harden Windows and Linux with platform-specific controls, including restricting RDP and SSH and enabling disk encryption and security controls.
- Centralize audit logs, set retention policies, synchronize system clocks, and alert on high-priority events.
- Use established baselines such as CIS Benchmarks, NIST guidance, or DISA STIGs; audit configurations regularly and document exceptions.
- Treat hardening as an ongoing process: inventory assets, test changes before deployment, and reassess systems as configurations drift.
Article Details
- Defense Focus
- Reduce attack surface and prevent unauthorized access or movement by establishing and maintaining secure system configurations.
- Detection Methods
- Assess system configurations against CIS Benchmarks or other documented baselines using configuration assessment tools.
- Run regular configuration audits, including quarterly reviews and reviews after major changes.
- Scan for known vulnerabilities and perform policy-compliance checks.
- Centralize and correlate audit logs, and alert on repeated failed logins, new local administrator accounts, and services installed outside change windows.
- Data Sources
- Authentication success and failure events
- Privilege escalation and privileged command events
- Account, group membership, and policy changes
- File-access changes
- Service installation events
- Inbound and outbound network traffic and firewall rule matches
- System configuration, installed software, and asset inventories
- Platforms
- Windows
- Linux
- AWS
- Azure
- Google Cloud
- Defensive Actions
- Disable default and inactive accounts, enforce strong passwords and MFA for privileged and remote access, and apply least privilege.
- Use default-deny firewall rules, close unused ports, disable insecure or unnecessary protocols and services, and restrict management interfaces to approved sources.
- Segment networks and restrict outbound connections from servers.
- Patch operating systems and third-party software on a defined schedule; track and replace or isolate end-of-life systems.
- Apply OS-specific controls, including disabling unnecessary Windows features and root SSH login, and enforcing SSH key-based authentication on Linux.
- Enable host-based protections, application allowlisting, and full-disk encryption where appropriate.
- Centralize audit logs, set retention periods, synchronize system clocks, and review alerts.
- Test hardening changes in staging before production deployment; document baselines and exceptions and reassess configurations regularly.
Vendors
Huntresssurface, but EDR catches what gets through. The two work together, not as substitutes for each other. Huntress gives IT teams and MSPs fully managed EDR with 24/7 monitoring by SOC analysts who investigate alertsMicrosoftMicrosoft Security Compliance Toolkit is Microsoft's free toolkit for applying and auditing security baselines on Windows systems, including GPOs aligned to Microsoft's security recommendations.QualysA scanner finds vulnerabilities; it doesn't evaluate how a system is configured. Nessus (Tenable) and Qualys are widely used options that include policy compliance scanning alongside vulnerability detection, andTenableassessment. A scanner finds vulnerabilities; it doesn't evaluate how a system is configured. Nessus (Tenable) and Qualys are widely used options that include policy compliance scanning alongside vulnerability
Products
AppArmorDisable root SSH login, enforce key-based auth, enable SELinux or AppArmor, configure auditdAppLockerConfigure AppLocker or Windows Defender Application Control (WDAC) to restrict which applications can run, and enable Credential Guard and Device Guard on supported hardware to protect against credential theft.AWSlogging), but cloud hardening requires cloud-specific tools and benchmarks. CIS publishes benchmarks for AWS, Azure, and Google Cloud.Azurebut cloud hardening requires cloud-specific tools and benchmarks. CIS publishes benchmarks for AWS, Azure, and Google Cloud.BitLockerDisable SMBv1, LLMNR, PowerShell v2; enable BitLocker, Credential Guard, and UAC; restrict RDPCredential GuardDisable SMBv1, LLMNR, PowerShell v2; enable BitLocker, Credential Guard, and UAC; restrict RDPDevice GuardConfigure AppLocker or Windows Defender Application Control (WDAC) to restrict which applications can run, and enable Credential Guard and Device Guard on supported hardware to protect against credential theft.Google Cloudhardening requires cloud-specific tools and benchmarks. CIS publishes benchmarks for AWS, Azure, and Google Cloud.LinuxLinux-specific hardeningMicrosoft WindowsWindows-specific hardeningSELinuxDisable root SSH login, enforce key-based auth, enable SELinux or AppArmor, configure auditdWindows DefenderLLMNR, NetBIOS over TCP/IP, and Windows Script Host if your environment doesn't rely on it. Enable Windows Defender or an equivalent endpoint protection solution, and keep definitions up to date.Windows Defender Application Control (WDAC)Configure AppLocker or Windows Defender Application Control (WDAC) to restrict which applications can run, and enable Credential Guard and Device Guard on supported hardware to protect against credential theft.
Tools
AnsibleAnsible is an agentless automation tool that applies hardening configurations across Linux and Windows systems using playbooks. The community maintains CIS Benchmark hardening roles via dev-sec.io.auditdDisable root SSH login, enforce key-based auth, enable SELinux or AppArmor, configure auditdChefPuppet and Chef are solid alternatives for teams already using these platforms for infrastructure management, with hardening automation supported through community modules.CIS-CAT LiteCIS-CAT Pro scans systems against CIS Benchmarks and produces a scored report showing what passes, what fails, and what needs attention. CIS-CAT Lite is a free version with limited benchmark coverage.CIS-CAT ProCIS-CAT Pro scans systems against CIS Benchmarks and produces a scored report showing what passes, what fails, and what needs attention. CIS-CAT Lite is a free version with limited benchmark coverage.Group PolicyGroup Policy is the native way to enforce hardening settings across domain-joined Windows systems at scale, with no additional tooling required.iptablesEnable and configure a host-based firewall (iptables or nftables) with default-deny rulesMicrosoft Security Compliance ToolkitMicrosoft Security Compliance Toolkit is Microsoft's free toolkit for applying and auditing security baselines on Windows systems, including GPOs aligned to Microsoft's security recommendations.Nessusassessment. A scanner finds vulnerabilities; it doesn't evaluate how a system is configured. Nessus (Tenable) and Qualys are widely used options that include policy compliance scanning alongsidenftablesEnable and configure a host-based firewall (iptables or nftables) with default-deny rulesOpenSCAPOpenSCAP is an open-source option that assesses systems against SCAP-formatted content, including DISA STIGs and NIST checklists.PuppetPuppet and Chef are solid alternatives for teams already using these platforms for infrastructure management, with hardening automation supported through community modules.QualysA scanner finds vulnerabilities; it doesn't evaluate how a system is configured. Nessus (Tenable) and Qualys are widely used options that include policy compliance scanning alongside vulnerability detection, and