What is CIS hardening? Basic hardening guidelines

Imagine waking up to a cyberattack that costs your business millions. In 2023, cybercrime caused $9.22 trillion in losses, with the average data breach costing $4.88 million. Shockingly, 46% of companies paid ransom after ransomware attacks. ^[1] Cybersecurity isn’t just an IT concern, it’s a business imperative and CIS hardening is a key component of cybersecurity.

Cyberattacks are growing in frequency and sophistication, and organizations must proactively safeguard their systems, data, and reputation. One of the most effective ways to achieve this is through CIS hardening, a standardized process designed to secure IT systems by reducing vulnerabilities and misconfigurations.

CIS, or the Center for Internet Security, is a nonprofit organization that provides free and community-driven security best practices through its CIS Benchmarks. These guidelines have become globally recognized for their effectiveness in protecting systems against emerging cyber threats. 

Let’s explore what CIS hardening is, why it is essential for cybersecurity, and what are the basic hardening guidelines across different environments. 

What is CIS hardening?

CIS Hardening is the process of configuring systems, applications, and networks to eliminate or reduce vulnerabilities. It is based on the CIS Benchmarks, a set of globally recognized best practices for securing IT assets. These benchmarks provide detailed instructions on how to configure systems in a secure manner, ensuring that they are less susceptible to cyberattacks.

CIS controls and their role

CIS hardening builds upon the CIS Controls, a prioritized framework of cybersecurity best practices. These controls help organizations focus on the most critical areas to defend against cyber threats. For example, CIS may recommend measures such as limiting administrative privileges, implementing strong authentication mechanisms, and ensuring that systems are continuously updated with the latest security patches.

By adhering to CIS hardening practices, organizations can integrate these best practices into their cybersecurity and compliance efforts. The result is a consistent, proactive approach that not only meets regulatory requirements but also improves the overall resilience of IT systems.

Why is CIS hardening important?

Implementing CIS hardening is not just a matter of following guidelines; it is a strategic step toward strengthening your cybersecurity posture. Here’s why it’s crucial:

• Reduces attack surface:
  Properly configured systems minimize potential entry points for attackers. CIS hardening reduces the number of vulnerabilities and misconfigurations that cybercriminals can exploit.
  
• Strengthens compliance:
  Many industries face stringent regulatory requirements, such as NIST, ISO 27001, GDPR, PCI-DSS, and HIPAA. By following CIS benchmarks, organizations align with these regulations and demonstrate due diligence in protecting sensitive data.
  
• Prevents cyberattacks:
  With the increasing sophistication of cyber threats, from ransomware to phishing, hardening measures help prevent unauthorized access, malware, and insider threats.
  
• Improves system performance:
  These hardening guidelines secure systems and often lead to performance improvements. Eliminating unnecessary services and processes can reduce system overhead, resulting in faster and more reliable performance.
  
• Simplifies security management:
  CIS guidelines provide a structured approach that is easy to implement across various environments. This structure makes it easier for organizations to manage security consistently and effectively.

In summary, CIS hardening is about creating a secure baseline for your IT infrastructure. It helps you stay ahead of cybercriminals, maintain compliance, and ensure your systems perform optimally while reducing overall risk.

Basic CIS hardening guidelines

​In 2024, the global average cost of a data breach reached $4.88 million, marking a 10% increase from the previous year.^[2] As cyber threats become more sophisticated and costly, hardening your IT environment is a necessity. In this section, we outline the essential guidelines for CIS hardening, covering general measures, operating system hardening, network hardening, and cloud security. Following these guidelines can help you build a robust defense against cyber threats.

1. General hardening guidelines

Before getting into system-specific details, consider these general practices:

• Keep systems updated:
  Regularly apply security patches and software updates. This minimizes the risk of vulnerabilities that have been discovered and exploited in outdated versions.
  
• Restrict administrative access:
  Follow the principle of least privilege (PoLP). Only grant users the minimum permissions necessary to perform their roles, reducing the potential for accidental or malicious misuse of privileges.
  
• Disable unused services:
  Turn off any unnecessary applications and services. Each running service can be a potential entry point for attackers, so limiting them reduces your overall attack surface.
  
• Implement strong authentication:
  Use multi-factor authentication (MFA) and enforce strong password policies. This adds an extra layer of protection against unauthorized access.
  
• Enable logging and monitoring:
  Configure systems to collect logs and monitor for suspicious activities. Effective logging helps in the early detection of anomalies and supports forensic investigations after incidents.

2. Operating system hardening

One key approach is using a unified endpoint management or MDM solution to enforce security policies, deploy updates, and control app installations across all devices. 

• Disabling unnecessary services, ports, and remote access features helps reduce attack surfaces. This includes Windows services like SMBv1 and Print Spooler, Linux network services like Telnet and FTP, and macOS remote login features such as SSH and screen sharing. 

• Encryption plays a vital role in securing sensitive data. Windows BitLocker, macOS FileVault, iOS device encryption, and Android file-based encryption ensure that data remains protected even if devices are lost or stolen. 

• Strong authentication practices, including complex passwords, biometric security (Face ID, Touch ID, fingerprint recognition), and two-factor authentication (2FA), add additional layers of security. 

• Built-in security tools like Windows Defender, Google Play Protect, and macOS Gatekeeper help prevent malware threats. Firewall configurations across all platforms control unauthorized network access. 

• Regular software updates and security patching are crucial in addressing vulnerabilities, ensuring that devices stay protected against evolving threats. 

By enforcing these hardening strategies across all operating systems, organizations can strengthen their cybersecurity posture, maintain compliance, and protect sensitive information against potential cyber risks.

3. Network hardening

While operating systems form the core of an IT environment, network security is equally crucial in defending against cyber threats. A well-hardened network prevents attackers from exploiting vulnerabilities, protects data in transit, and ensures that only authorized users and devices can access critical resources. Below are essential network hardening practices:

1. Configure firewalls properly

Firewalls serve as the first line of defense by filtering network traffic based on security policies. To enhance protection:

• Allow only necessary traffic: Define strict inbound and outbound rules using a default-deny approach where only explicitly allowed traffic is permitted.
  
• Implement a layered firewall strategy: Use network firewalls and host-based firewalls on individual endpoints for an added layer of defense.
  
• Apply deep packet inspection (DPI): This analyzes packet content for malware, command-and-control traffic, or other malicious payloads.
  
• Regularly audit firewall rules: Remove outdated, redundant, or overly permissive rules to prevent potential attack vectors.

2. Use VPNs for secure remote access

A Virtual Private Network (VPN) ensures secure data transmission between remote users and corporate resources by encrypting communication channels.

• Implement VPN tunneling: Use VPN tunneling protocols to encapsulate and encrypt data packets, preventing eavesdropping or interception by malicious users. There are two main types:
  
  • Split tunneling: Routes only specific traffic through the VPN while other traffic goes directly to the internet (riskier but improves performance).
    
  • Full tunneling: Directs all network traffic through the VPN, ensuring complete security but potentially affecting speed.
    
• Use strong encryption protocols: Choose IPSec, OpenVPN, or WireGuard with AES-256 encryption for maximum security.
  
• Adopt a Zero Trust approach: Do not automatically trust any user or device. Require multi-factor authentication (MFA), endpoint security checks, and least-privilege access before granting VPN connectivity.
  
• Monitor VPN activity: Log and analyze VPN connections to detect anomalies such as unusual login locations, excessive session durations, or failed login attempts.
  
• Use VPN interlinking for secure network expansion: Link multiple VPNs together to create a unified, encrypted network across different locations or cloud environments, ensuring seamless and secure data flow.

3. Disable unused network protocols

Many legacy and unnecessary network protocols introduce security risks if left enabled. To minimize threats:

• Turn off outdated protocols: Disable SMBv1, Telnet, RDP (if not needed), and older SSL/TLS versions to close known vulnerabilities.
  
• Restrict broadcast and multicast traffic: Prevent attackers from exploiting these for reconnaissance or amplification attacks.
  
• Enforce secure alternatives: Replace FTP with SFTP, Telnet with SSH, and outdated VPN protocols with modern encryption standards.
  
• Conduct regular network audits: Identify and disable any unused services or ports that could be exploited by attackers.

4. Monitor Network Traffic

Continuous monitoring is essential to detect, analyze, and respond to security threats before they cause damage.

• Deploy Intrusion Detection and Prevention Systems (IDPS): These monitor network traffic for known attack patterns and can automatically block suspicious activity.
  
• Enable centralized logging and analysis: Use Security Information and Event Management (SIEM) tools to collect, correlate, and analyze logs for real-time threat detection.
  
• Use anomaly detection: Behavioral analysis tools can detect unusual traffic patterns indicative of malware infections, insider threats, or active attacks.
  
• Implement strict network segmentation: Divide the network into isolated segments to limit an attacker’s lateral movement in the event of a breach.

By implementing these network hardening techniques, organizations can strengthen their cyber defenses, ensure secure communications, and significantly reduce the risk of unauthorized access or data breaches.

4. Cloud security hardening

As more organizations move to the cloud, hardening cloud environments is increasingly critical. These guidelines help secure your cloud-based assets:

1. Implement strong Identity and Access Management (IAM) policies

Identity and Access Management (IAM) is the backbone of cloud security, ensuring that only authorized users and services have access to critical resources. To enhance IAM security:

• Follow the Principle of Least Privilege (PoLP): Grant users and applications only the minimum permissions necessary to perform their tasks. Regularly audit and remove unused permissions.
  
• Use Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC): Define granular permissions based on user roles, job functions, or attributes.
  
• Enable Identity Federation: Integrate with SSO (Single Sign-On) providers and use OAuth, SAML, or OpenID Connect to centralize authentication across cloud services.
  
• Monitor IAM activity: Track logins, permission changes, and access patterns using CloudTrail (AWS), Audit Logs (GCP), or Security Command Center (Azure).
  
• Implement Just-In-Time (JIT) access: Allow temporary privilege escalation only when necessary, reducing the risk of persistent access exploitation.

2.  Enforce Data Encryption

Data encryption is essential for protecting sensitive information from unauthorized access, whether stored data or in transit data. Best practices include:

• Encrypt data at rest: Use strong encryption standards such as AES-256 to protect stored data on cloud storage services.
  
• Encrypt data in transit: Enforce TLS 1.2/1.3 encryption to secure data transfers between cloud applications, users, and on-premise infrastructure.
  
• Use customer-managed keys (CMKs): Instead of relying solely on cloud provider-managed keys, leverage KMS (Key Management Service) solutions for enhanced control.
  
• Regularly rotate encryption keys: Implement key rotation policies to reduce the risk of compromised encryption keys being misused.

3. Use Security Groups & Access Control Lists (ACLs)

Cloud network security must be tightly controlled to limit exposure to threats. To achieve this:

• Configure security groups: Security groups act as virtual firewalls, restricting inbound and outbound traffic based on predefined rules. Set rules to allow only necessary traffic and deny everything else by default.
  
• Implement Network Access Control Lists (ACLs): Use ACLs to define IP-based access restrictions and enforce traffic filtering at the subnet level.
  
• Apply microsegmentation: Isolate cloud workloads and restrict communication between services using VPCs (Virtual Private Clouds), subnets, and private endpoints.
  
• Monitor network activity: Use VPC Flow Logs, Azure Network Watcher, or Google Cloud VPC logs to track network traffic and detect anomalies.

4. Enable Multi-Factor Authentication (MFA)

Multi-Factor Authentication (MFA) is a critical safeguard against unauthorized access, even if credentials are compromised. To strengthen MFA implementation:

• Require MFA for all privileged accounts: Enforce MFA for administrators, IAM users, and DevOps engineers managing cloud resources.
  
• Use phishing-resistant authentication: Opt for FIDO2-based security keys or app-based authenticators instead of SMS-based MFA.
  
• Enforce conditional access policies: Require MFA only when accessing resources from untrusted locations, new devices, or risky login attempts.
  
• Monitor MFA usage: Regularly review MFA logs for suspicious activity, such as multiple failed attempts or new device enrollments.

By enforcing these cloud security best practices, organizations can significantly reduce the risk of breaches, data leaks, and unauthorized access to cloud resources.

How to implement CIS hardening effectively?

Implementing CIS hardening is not a one-day project. It requires ongoing effort and regular review. Here are some effective strategies:

• Conduct security assessments: Regularly assess your security posture to identify weak configurations and vulnerabilities. This proactive approach will help you stay ahead of emerging threats.
  
• Use CIS-CAT Pro: Consider using the CIS Configuration Assessment Tool (CIS-CAT Pro) provided by CIS to evaluate how well your systems adhere to the benchmarks. This tool can help pinpoint areas that require immediate attention.
  
• Automate hardening processes: Use compliance automation tools to streamline configuration management. Automation ensures that security settings remain consistent across all systems, reducing human error and saving valuable time.
  
• Continuously monitor and update configurations: Cyber threats are constantly evolving, so your security measures must evolve too. Regularly review and update your hardening guidelines to incorporate new best practices and address emerging risks.

By implementing these steps, you can create an effective CIS hardening strategy that adapts to changes in technology and threats.

Is your security future-proof? CIS hardening is the key

CIS hardening involves configuring systems according to CIS Benchmarks to minimize vulnerabilities and strengthen security. Misconfigurations expose critical infrastructure to cyber threats, making it essential to enforce strict security settings, disable unnecessary services, and apply standardized controls.

A strong cybersecurity posture requires ongoing assessment and proactive security measures. Organizations must continuously evaluate their security strategy and take necessary steps to maintain compliance with CIS Benchmarks. 

Scalefusion Veltar provides solutions to CIS hardening, enhancing compliance, and strengthening cybersecurity defenses. Register your interest today and explore how Scalefusion Veltar can help you.

Reference:
1. PacketLabs
2.IBM Cost of Data Breach Report 2024