Windows and Linux Server Hardening: Comprehensive Checklist

Server hardening is the identification of security vulnerabilities in your Linux or Windows servers in order to configure changes and other remediation steps required to reduce these vulnerabilities. Server hardening involves applying the principles of system hardening to servers specifically.

The goal of server hardening is to make your server a more difficult target for hackers, thereby protecting your operations and saving you money in the long run. However, server hardening has the added advantage of improving your organization’s compliance with industry and state information security regulations.

Your server hardening process starts with a checklist that outlines the steps you should take to protect your Windows or Linux server against common security threats. These steps are based on guidelines developed by cybersecurity experts and codified by bodies such as the National Institute of Standards and Technology (NIST) and the Center for Internet Security (CIS). These server hardening checklist items are broad strokes that apply to Windows, Linux, and other types of servers. If you want a detailed breakdown, the NIST and CIS benchmarks have the resources you need.

1. Account Policies

User accounts are identities created to allow authenticated access to a server or related system. Different user accounts have different levels of access to core functions of the server, with administrator accounts having the highest level of access.  Enforcing a strong password policy for these accounts is vital to maintain security. 

Here’s how to set them up:

a. Password Policy

• Minimum length: 12 characters
• Complexity: Mix of uppercase, lowercase, numbers, and symbols
• Expiration: Every 90 days
• History: Prevent reuse of last 10 passwords

b. Account Lockout

• Threshold: 5 failed attempts
• Duration: 30 minutes
• Counter reset: After 15 minutes

You should also implement two-factor authentication (2FA) for all accounts, particularly for those with administrative privileges. This additional security layer significantly reduces the risk of unauthorized access, even if passwords are compromised. 

In addition, conduct regular account audits on a quarterly basis. During these reviews, disable or remove any unused accounts, eliminate unnecessary default accounts, and apply the principle of least privilege by ensuring each user has only the access required for their role.

2. User Account Security Hardening

Implementing additional user account security measures is crucial for robust server protection beyond basic account policies. These steps focus on minimizing potential vulnerabilities associated with user accounts and their privileges. Here’s how you can further enhance security:

a. Separate user accounts

• Create standard user accounts for daily tasks
• Use administrator accounts only when necessary for system changes
• Implement separate accounts for different purposes (e.g., email, database access)

b. Built-in account management

• Rename built-in administrator accounts (e.g., ‘Administrator’ on Windows or ‘root’ on Linux)
• Disable or remove unnecessary built-in accounts, especially those with elevated privileges

c. Account monitoring

• Implement logging of user account activities, especially for privileged accounts
• Regularly review these logs for suspicious activities
• Set up alerts for unusual login patterns or access attempts

You should also consider implementing time-based restrictions on when users can log in, particularly for administrative accounts. This can help prevent potential attackers from accessing off-hours. Additionally, use group policies (on Windows) or similar mechanisms (on Linux) to centrally manage and enforce user account settings across multiple servers.

3. User Rights Management

Effective user rights management is critical for maintaining server security. It involves controlling access to system resources and limiting the potential impact of compromised accounts. Implement these measures to enhance your server’s security:

a. Access Control Lists (ACLs)

• Implement and regularly review ACLs for files, directories, and system resources
• Use role-based access control (RBAC) to assign permissions based on job roles

b. Privileged Access Management

• Implement a system for managing privileged access (e.g., using a PAM solution)
• Enable just-in-time privileged access, providing elevated privileges only when needed

c. Regular Reviews

• Conduct periodic reviews of user rights and permissions
• Remove or adjust access rights that are no longer necessary

d. Separation of Duties

• Ensure no single user has excessive privileges
• Separate critical system functions among different users or roles

Enable comprehensive logging of user activities, especially for privileged accounts. Regularly review these logs for unusual or unauthorized activities. Remember, the goal is to restrict access to administrator-level accounts and assign users just enough privileges to perform their job functions effectively.

4. Updates and Patches

Keeping your servers up-to-date with the latest security patches and updates is crucial for maintaining a strong security posture. To ensure your servers remain protected, try these optimizations:

a. Automated Updates

• Configure automatic updates for your operating system
• Set up automatic updates for third-party applications running on your servers

b. Update Policies

• Develop clear policies for applying updates, including scheduling and testing procedures
• Implement a centralized patch management system for multiple servers

c. Testing and Verification

• Create a test environment to check updates before applying to production servers
• Verify successful installation and system functionality after applying updates

d. Emergency Procedures

• Develop a process for quickly applying critical security patches outside regular schedules
• Maintain a rollback plan in case an update causes unforeseen problems

Regularly conduct security vulnerability scans to identify any missing patches or security updates. Monitor for available updates, successful or failed installations, and systems that are out of date. Remember, while keeping systems updated is crucial, it’s equally important to do so in a controlled and tested manner to avoid disruptions to your operations.

5. Network Security

Your network firewall is your first line of defense against all external attacks, so make sure it is enabled and set it up to block all inbound traffic by default. Implement these measures across key areas:

a. Network Configuration

• Implement network segmentation to isolate critical systems
• Disable unnecessary network services and protocols
• Use secure protocols (e.g., SSH instead of Telnet, SFTP instead of FTP)
• Set up a VPN for secure remote access to server resources

b. Firewall Configuration

• Enable and configure a physical firewall to block all inbound traffic by default
• Regularly review and update firewall rules
• Allow only necessary incoming network traffic for your operations
• Implement application layer filtering and stateful packet inspection
• Set up logging for firewall activities and alerts for potential security events

c. NTP Configuration

• Configure Network Time Protocol (NTP) for accurate time synchronization
• Use trusted NTP servers, preferably internal ones if available
• Implement security measures for NTP, such as authentication

Regular monitoring of network activity is essential. Set up tools to detect and alert on unusual network behavior or potential security threats. Remember, a well-configured network is your first line of defense against external attacks.

6. Antivirus & Software Security

Antivirus and anti-malware programs protect your systems by actively scanning for malicious software and removing them when detected. Here’s what you can do to optimize your server security on this front:

• Install reputable antivirus software on all servers, configuring daily definition updates and automated full-system scans during off-peak hours.
• Enable real-time protection features to catch threats as they appear.
• Use a centralized management console for consistent deployment and monitoring across multiple servers.
• Implement application whitelisting to allow only approved software to run.
• Enable behavior-based detection to catch unknown threats.
• Utilize sandboxing to test suspicious files before allowing them on production servers.
• Develop an incident response plan for potential malware infections.

These measures create a robust defense against malware, significantly enhancing your server’s security posture. Regular updates and vigilant monitoring are key to maintaining effective protection.

7. Application and Service Configuration

Properly configuring applications and services is crucial for maintaining server security. It helps minimize vulnerabilities and reduces the attack surface that malicious actors could exploit. This involves hardening both applications and their associated databases.

a. Application Hardening

• Keep all applications up-to-date with the latest security patches
• Remove or disable unnecessary features and services
• Configure applications to run with the least privileges necessary
• Implement input validation to prevent injection attacks
• Use secure coding practices when developing custom applications
• Enable logging and monitoring for all critical application activities

b. Database Hardening (for application databases)

• Use strong authentication methods for database access
• Encrypt sensitive data stored in databases
• Regularly patch and update database software
• Implement proper access controls and limit user privileges
• Enable database activity monitoring and auditing
• Use secure protocols for database connections

These measures work together to secure your applications and their data. For example, input validation in the application prevents SQL injection attacks on the database. Similarly, limiting application privileges helps enforce database access controls.

8. Operating System Hardening

Operating System (OS) hardening is crucial for reducing your server’s vulnerability surface. Start by regularly applying security patches and updates to the OS. Then, focus on these key areas:

• Disable or remove unnecessary services, features, and default user accounts 
• Implement strong password policies and account lockout procedures 
• Configure system-wide security settings (e.g., disable autorun)
• Use secure protocols like SSH for remote administration and enable host-based firewalls. Implement file system encryption where appropriate and set up comprehensive logging and monitoring.

Additional important steps include:

• Restricting access to important system files and directories 
• Disabling unnecessary network ports 
• Using security templates from trusted sources

Also, remember to regularly audit your system to ensure compliance with security policies. These measures collectively strengthen your OS, forming a solid foundation for overall server security.

9. Feature and Role Configuration

Feature and Role Configuration involves managing the specific functions and services your server provides. Proper configuration is critical because each enabled feature or role can potentially increase your server’s attack surface.

To harden your server’s features and roles:

• Conduct an inventory of all installed features and roles
• Remove or disable unnecessary features and roles
• Enable only required network ports for each role
• Implement proper access controls for each feature and role
• Configure logging and monitoring for all active features and roles
• Regularly review and update configurations
• Test all changes in a non-production environment first

For essential features and roles, you can configure them to run with least privilege, apply all relevant security patches and updates, and implement role-specific security best practices.

10. Server Hardening

Server hardening enhances security through various configurations and best practices, reducing the server’s attack surface. Begin by securing physical access to the server and utilizing hardware-based security features like Trusted Platform Module (TPM).

Key steps include:

• Configuring BIOS/UEFI settings securely with strong passwords 
• Disabling unnecessary hardware components and ports
• Implementing full disk encryption 
• Using secure boot mechanisms

In addition, regularly update firmware and drivers to patch potential vulnerabilities. As part of ongoing maintenance, monitor hardware health and performance, ensuring proper ventilation and cooling. For critical systems, consider implementing redundant power supplies to prevent downtime due to power failures.

Maintaining an up-to-date hardware inventory and implementing a hardware lifecycle management plan are crucial for long-term security. These measures, when combined with regular security audits, significantly strengthen your server’s resilience against potential threats and unauthorized access.

11. Registry Configuration

Registry configuration is crucial for Windows servers, as it controls system and application settings. Proper configuration prevents unauthorized changes and protects critical system information. Start by restricting access to registry editing tools and regularly backing up the registry before making changes.

To enhance registry security, consider implementing these measures:

• Use Group Policy to enforce secure registry settings
• Implement registry auditing to track changes 
• Disable remote registry access if not required 
• Encrypt sensitive registry keys

Additionally, monitor critical registry keys for unauthorized changes and remove obsolete entries regularly. It’s also beneficial to use Windows Security Templates to apply predefined security policies, which can help maintain consistent and secure configurations across multiple servers.

Furthermore, modify registry permissions to limit access to sensitive areas and disable AutoRun to prevent programs from being executed automatically. Finally, conduct regular scans for malicious registry entries. These combined measures significantly bolster your server’s security posture.

12. Encryption

Encryption is the process of encoding data to prevent unauthorized access. It’s essential for protecting sensitive information both at rest and in transit.

Steps to implement strong encryption:

• Use industry-standard encryption protocols (e.g., AES, RSA)
• Implement full-disk encryption for all servers
• Encrypt sensitive data stored in databases
• Use encrypted protocols for all network communications (e.g., HTTPS, SSH, SFTP)
• Implement email encryption for sensitive communications
• Use VPN for remote access to server resources
• Regularly rotate encryption keys
• Securely store and manage encryption keys
• Use hardware security modules (HSMs) for key storage when possible
• Encrypt backups and archived data
• Implement encryption for cloud storage and services
• Use encrypted file systems for sensitive directories

13. Access Management

Access management controls who can access your server and what they can do. It’s crucial for preventing unauthorized access and limiting potential damage from compromised accounts.

Key steps for robust access management:

• Use the principle of least privilege for all accounts
• Implement multi-factor authentication (MFA)
• Regularly audit and review user access rights
• Set up a formal process for granting and revoking access
• Use strong, unique passwords for all accounts
• Monitor and log all access attempts

Extending these principles to remote access, which requires additional security measures, is possible with these actions:

• Use VPN for secure remote connections
• Limit remote access to specific IP ranges when possible
• Implement jump servers for indirect access to critical systems
• Use secure protocols (SSH, RDP with Network Level Authentication)
• Enable detailed logging for all remote sessions
• Regularly patch and update remote access software

14. General Security Settings

General security settings encompass a broad range of configurations that enhance overall server security. Begin by disabling or removing all unnecessary services and applications to reduce the attack surface. Configure session timeouts for idle users and restrict USB and external storage device access to prevent unauthorized data transfers. Enable and configure system auditing and logging to track activities and detect potential security incidents.

Set up intrusion detection and prevention systems to safeguard against attacks. Implement file and folder permissions based on the principle of least privilege, ensuring users only have access to what they need. Enable and configure system restore points to allow quick recovery in case of issues.

Key additional steps include:

• Implementing and maintaining strong password policies
• Disabling support for unnecessary network protocols
• Configuring automatic screen locking
• Disabling autorun/autoplay features
• Regularly updating and patching all software and firmware

15. Backups & Recovery

Your server hardening checklist would not be complete without a proper backup and recovery plan. Backups can protect your servers from data loss, ransomware attacks, and other disaster-level events that affect information security. 

Implementing a comprehensive backup plan is an essential component of server hardening. Here are the key steps for effective backups and recovery:

• Document backup and recovery procedures
• Implement automated, continuous backups
• Adopt the 3-2-1 backup strategy: (keep 3 copies of your data, store backups on 2 different media types, keep 1 copy offsite or in the cloud)
• Encrypt backups
• Regularly test backup integrity and recovery processes
• Implement backup monitoring and alerting
• Secure backup infrastructure

16. Audit Policies and Documentation

Comprehensive logging, monitoring, and documentation are critical for maintaining server security and facilitating incident response. Implementing robust audit policies helps detect security threats and troubleshoot system issues effectively.

Essential steps for audit policies and documentation:

• Configure comprehensive system logging
• Implement log retention and rotation policies
• Enable and configure system auditing
• Implement real-time log monitoring and alerting
• Regularly review and analyze logs
• Maintain detailed documentation
• Conduct regular security audits
• Establish and document incident response procedures
• Align logging and auditing practices with industry standards (e.g., PCI DSS, HIPAA)

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Implementing a robust server hardening strategy is something every business should prioritize to protect sensitive data, ensure system reliability, and mitigate the risk of cyberattacks, to safeguard your organization’s reputation and operational continuity.

By following this comprehensive checklist, you’ve taken significant steps towards fortifying your Windows and Linux servers against potential threats, whether you’re using VPS hosting, dedicated servers, or cloud-based hosting solution.

For those seeking to further enhance their server security or looking for managed hosting solutions with built-in security measures, consider exploring our Liquid Web hosting plans. Our team of experts is ready to assist you in creating a secure, robust hosting environment tailored to your needs. Check out Liquid Web hosting plans today to discover how to transform your server security strategy!