Top Windows Server Security Practices Explained

By Alex Carter on October 8, 2024

Securing a Windows Server is a critical step in maintaining the overall integrity of your organization’s IT infrastructure. Servers often store sensitive data, host business-critical applications, and provide access to internal systems. Without proper security measures, these servers can become prime targets for unauthorized access and malicious attacks.

How to Properly Secure a Windows Server

When integrating a server into your organization’s IT infrastructure, security should come first. To help keep your Windows server secure, here’s a detailed checklist of key security procedures and recommended practices for minimizing possible dangers.

If you’re choosing between platforms, understanding the differences in security setups and administration between Linux and Windows Server will help you select the best option for your company.

Initial Server Hardening Procedures

Securing a server begins before the operating system is installed. To create a good security foundation, start by undertaking the following actions:

• Maintain a complete inventory of all physical and virtual servers in your firm;
• Isolate new servers from both internal networks and internet access until they are completely hardened;
• To prevent unauthorized modifications to the BIOS or firmware settings, give a strong password;
• Turn off automated administrative logins to the recovery console to prevent misuse;
• Change the boot sequence so that the server cannot start from unapproved external media.

Feature and Role Management

A critical step in strengthening Windows server security is to remove all unnecessary features and roles that are not essential to the server’s operational purpose. Eliminating unneeded roles helps minimize the server’s attack surface and contributes to a simpler, more secure configuration that’s easier to maintain and troubleshoot.

Application and Service Optimization

Similarly, it’s important to limit the number of installed applications, active services, and communication protocols on each server. Avoid installing additional web browsers and restrict internet access for users to the bare minimum needed for operational tasks.

Reducing the number of running services and applications decreases the potential for vulnerabilities and simplifies ongoing patch and maintenance efforts.

Network Settings and Isolation

The network setup directly influences the security posture of your Windows servers. To enhance protection:

• Separate servers from untrusted networks or traffic sources using techniques like VLANs, subnet segmentation, or dedicated network zones. This limits their exposure to external and internal threats;
• Verify that DNS entries and hostname configurations are accurate and secure to prevent tampering or misdirection;
• Apply IP-based access control policies and implement filtering rules to strictly define which IP addresses or subnets are permitted to communicate with the server;
• When remote access is necessary, restrict RDP access to specified IP ranges only, minimizing potential intrusion paths;
• Disable NetBIOS over TCP/IP and LMHosts lookup unless legacy systems explicitly require them.

Accurate Time Synchronization (NTP)

Accurate time settings are vital for tracking events and protecting against time-based threats like replay attacks.

Assign a designated server to act as the central time source and sync it with a reliable atomic clock. All other servers and endpoints should be configured to synchronize exclusively with this internal time server to maintain consistency and reduce spoofing risk.

Registry Hardening

Registry configuration is an important part of server security and should be handled with care. The Remote Registry service should be disabled unless it is required for specific tasks, and if enabled, strict access controls must be applied. To reduce the risk of unauthorized access, disable the “NullSessionPipes” and “NullSessionShares” settings, which otherwise allow anonymous connections to network resources. Only authorized administrators and essential system processes should have permission to modify critical registry keys.

Data Encryption

Enable BitLocker to encrypt the operating system disk as well as any extra data volumes to protect sensitive data at rest and in transit. When individual file-level encryption is required, utilize the Encrypting File System (EFS). To safeguard data going between servers, use IPsec to encrypt network traffic and assist ensure confidentiality and integrity.

Access Controls and Permissions

Access control is a key component of server hardening. Use the concept of least privilege to guarantee that users and system processes only have the access privileges they require to accomplish their jobs. Avoid giving wide rights to groups like Everyone, and always evaluate and update group memberships. Allow only authenticated users to connect to the server over the network. Configure the system to support specific encryption types for Kerberos authentication. Prevent storage of LAN Manager (LM) hash values, as they present a security risk. Disable file and print sharing if it is not needed, and turn off the NTLMv1 protocol unless it is required for compatibility with legacy systems.

Remote Access Security

Remote Desktop Protocol (RDP) should be disabled unless it is necessary for specific administrative tasks. If enabled:

• Configure RDP to use the highest level of encryption available;
• Limit remote access permissions to only those users who require it to perform their roles;
• Strengthen security further by enabling multifactor authentication (MFA), reducing the risk of unauthorized logins even if credentials are compromised.

Core Security Measures for Windows Servers

To boost Windows server security, it’s important to apply a few basic hardening steps. Start by disabling access to removable media like USB drives to reduce the risk of data theft or malware infections. Set up a legal notice before login, such as “Unauthorized use of this computer and networking resources is prohibited”—to discourage misuse and support legal action if needed. Require the Ctrl+Alt+Del key combination for logins to ensure users are interacting with a trusted login screen. 

Also, configure the server to automatically end idle sessions after a set period to limit the risk of unauthorized access. If the server has enough RAM, you may want to disable the swap file to prevent sensitive data from being written to disk and to improve performance.

Firewall Configuration and Protection

The Windows Firewall is a critical security feature that safeguards the server against unauthorized access and harmful traffic. It should remain enabled at all times across all server profiles—Domain, Private, and Public. Each profile should be configured to block inbound connections by default. Only open the specific ports that are necessary for server functionality, and limit access to those ports using IP-based restrictions.

To reduce potential vulnerabilities, disable any firewall rules that are not required. Fewer enabled rules mean fewer open ports, which minimizes the server’s exposure. For ports that must stay open, such as those used for web hosting, allow access only from trusted IP addresses.

Commonly used firewall ports for Windows-based cloud servers hosting web applications include:

• Port 80 (HTTP) – for IIS websites or web applications;
• Port 443 (HTTPS) – for secure IIS websites or applications using SSL.

Keeping firewall rules simple and under control helps to reduce the danger of unwanted access and ensure that only needed network traffic reaches the server.

Think Twice Before Sharing Any Data

Sharing files on Windows might be dangerous if not done correctly. The server often opens ports 445 and 139 when file sharing is enabled. These ports are frequently the focus of illegal connection attempts, and their presence increases the possibility of unwanted access. Therefore, it is typically recommended to avoid using file sharing services unless absolutely required.

It’s crucial to keep an eye on and control the server’s software in addition to removing unnecessary file sharing. Every new software package may introduce new vulnerabilities or backdoors. Allow only trustworthy programs and prevent users from downloading or installing software that has not been properly reviewed and authorized.

Use Strong Passwords and Secure User Accounts

A server is just as secure as the credentials used to access it, therefore, enforcing a strong password policy is a critical step in preventing unauthorized logins and brute-force attacks. To make passwords more difficult to guess or break using automated methods, they should be at least 8 to 10 characters long and include a combination of uppercase and lowercase letters, digits, and special characters (such as!, #, $, and %). In addition, set password expiration policies for all user accounts, mandating periodic updates to limit the chance of compromised credentials being exploited over time and promote improved account hygiene throughout the business.

Once the server is operational and fully patched, configure user account settings to enhance security further. Disable the guest account on all servers, and either deactivate or rename the default Administrator account, resulting in a new administrator account with a different, non-default name. Reduce users and rights assigned to built-in groups such as Local System (NT AUTHORITY\System), Network Service (NT AUTHORITY\NetworkService), Administrators, Backup Operators, Users, and Everyone. For example, change the access control for the “Access this computer from the network” capability to exclude the Everyone group. 

Enforce stricter password criteria for administrative and system accounts—require passwords of at least 15 characters that include uppercase and lowercase letters, numbers, and special symbols—and mandate updates every 90 to 180 days. Establish an account lockout policy that adheres to best practice recommendations to guard against brute-force attempts. Disable anonymous SID/Name translation to complicate user identification for attackers, and promptly deactivate or delete accounts no longer in use. 

Finally, instruct server administrators to sign in using a local administrator account instead of a privileged domain account to minimize the potential impact of domain-wide security breaches.

Assign Separate Administrative Accounts

Grant administrative access only to trusted users. If multiple users require admin privileges, create individual admin accounts for each person. This ensures accountability, as activities can be traced to specific users rather than a shared admin account.

Secure SQL Server Instances

For Microsoft SQL Server, restrict port 1433 to the internal interface to minimize external attack risks. If external access is necessary, allow connections only from specific, trusted IP addresses used by developers.

For SQL Server Standard and Web editions, configure maintenance plans to export data to flat files regularly. These files can be backed up off the server, and old backups should be removed to conserve storage space.

Keep Windows Updated

Once the Windows Server operating system has been installed, apply the most recent updates promptly to decrease the risk posed by known vulnerabilities. Updates are available directly from Microsoft or through services like Windows Server Update Services (WSUS) and System Center Configuration Manager (SCCM).

To ensure long-term server security, activate notifications for newly published patches and deploy them immediately. However, each update, including hotfixes and service packs, must be extensively tested before being deployed in production to ensure compatibility and avoid unforeseen difficulties.

Establish a Reliable Backup and Recovery Plan

Implement a disaster recovery strategy by periodically creating cloud server images and storing them in Cloud Files with a retention policy of at least seven days. Test these backups by launching new server instances from the images and restoring individual files to confirm that your backup process is reliable and your data is recoverable.

Secure Your Application Code

Application code accessible over the Internet must be built with strong security measures. Developers should implement robust authentication and authorization protocols. Ensure all file permissions are correctly configured, and input validation is thoroughly enforced to prevent attackers from exploiting vulnerabilities and gaining unauthorized server access.

Conclusion

Securing a Windows Server involves applying clear configuration steps, maintaining regular updates, and limiting unnecessary access. By focusing on firewall settings, strong passwords, user account controls, and software restrictions, organizations can lower the risk of unauthorized activity and system compromise. Consistent monitoring and adherence to best practices help keep the server stable, protected, and aligned with security requirements.