Network firewall security: A complete guide

Network firewall security is a critical aspect of protecting IT infrastructure. In this guide, we will cover what a firewall is, its purpose in ensuring network security, how it works, best practices for firewall management, and common troubleshooting tips.

What is a firewall?

A firewall is a network security device that controls traffic to and from your network based on predetermined rules. It acts as a gatekeeper, analyzing data packets and determining whether they should be allowed or blocked. Firewalls prevent unauthorized access and protect sensitive data from cyberthreats.

What is the role of a firewall in network security?

A firewall acts as a barrier that blocks malicious traffic while allowing legitimate connections.

Key purposes of firewalls:

Traffic monitoring: Firewalls analyze incoming and outgoing traffic. This analysis helps network admins to identify suspicious activities, if any.

Access control: They enforce rules that specify which traffic is allowed, ensuring that only authorized users have access to the network.

Protection against cyberattacks: Firewalls help block malware, ransomware, and other forms of cyberattacks before they reach the network.

Network segmentation: Firewalls can be used to create segments in the network, which will help limit the spread of malware and enhance internal security. This requires some specific configuration and setup.

How does a network firewall work?

Firewalls filter network traffic based on a set of defined rules and policies, allowing legitimate data packets to pass through while blocking malicious or suspicious traffic. Network traffic is composed of data packets, which are small units of data transmitted across the network. Each packet contains three key components:

Header: Contains metadata about the packet, such as source IP address, destination IP address, protocol type (e.g., HTTP or TCP), and port numbers.

Payload: The actual data being transmitted (e.g., a file, request, or message).

Footer: Includes control information used for error detection and packet integrity.

Firewalls inspect these data packets to determine whether to allow or block them based on predefined security rules.

Here’s a step-by-step breakdown of how it operates:

• Packet filtering: When data packets arrive at the firewall, they are examined against a list of security rules.
• Inspection: The firewall checks the packet's header, including source and destination IP addresses, port numbers, and protocol type.
• Decision-making: Based on the inspection, the firewall decides whether to allow, reject, or drop the packet.
• Logging: All activities are logged, providing an audit trail of what traffic was blocked or permitted.

Best practices for ensuring network firewall security

To ensure optimal network security through implementation of firewalls, follow these best practices:

• Regular updates: Keep your firewall software and firmware up to date to protect against the latest threats.
• Implement a strong rule set: Define clear rules based on the principle of least privilege, allowing only necessary traffic .
• Enable intrusion detection and prevention: Use firewalls with integrated IDS and IPS features to detect and block malicious activities.
• Conduct regular audits: Periodically review firewall rules and logs to identify any misconfigurations or anomalies.
• Use network segmentation: Divide the network into secure zones and control traffic between these zones using firewalls.

Common troubleshooting issues for network firewalls

Firewalls can encounter issues that disrupt normal operations. Here are some common problems and their solutions:

Blocked legitimate traffic: Misconfigured rules can block valid traffic. Review the rule set and allowlist necessary IPs or ports.

Firewall performance issues: High traffic volumes or outdated hardware can cause slow performance. Upgrade hardware or optimize rules to reduce load.

Connection timeouts: Incorrect timeout settings may terminate legitimate sessions prematurely. Adjust session timeouts for critical applications.

Firewall logging overload: Excessive logging can overwhelm storage. Configure log rotation and filter unnecessary logs.

Security use cases for network firewalls

Network firewalls play a crucial role in protecting IT environments from a variety of sophisticated cyberthreats. Below are some use cases that highlight how they enhance security in different scenarios.

1) Securing inbound and outbound traffic

Firewalls enforce strict controls on both inbound and outbound network traffic. By utilizing deep packet inspection, firewalls examine not only the packet headers but also the data payload. This level of scrutiny helps:

• Prevent unauthorized access: Inbound traffic from unknown or suspicious IP addresses is blocked automatically, minimizing the risk of intrusions.
• Control data exfiltration: Firewalls monitor outbound traffic and enforce policies to detect unusual data transfers, preventing potential data breaches or leaks.

Example: If a device in the network suddenly starts transmitting large volumes of data to an unfamiliar external IP, the firewall triggers an alert and blocks the traffic, mitigating data exfiltration risks.

2) Segmenting the network for enhanced security (microsegmentation)

Firewalls enable network segmentation and microsegmentation, creating isolated zones within the network. This minimizes the risk of lateral movement by attackers who have breached the perimeter.

• Policy-based segmentation: Allows for granular control over which devices and users can access specific network segments.
• Zero Trust implementation: Enforces the principle of "never trust, always verify," requiring continuous verification of all devices trying to access different segments.

Example: In a segmented network, if an IoT device is compromised, the firewall limits its access to a specific zone, preventing the attacker from moving laterally to critical servers or databases.

3) Preventing DDoS attacks

Firewalls equipped with distributed denial-of-service (DDoS) protection mechanisms can detect and mitigate traffic spikes caused by DDoS attacks. These firewalls use techniques such as rate limiting, traffic shaping, and packet dropping to reduce the impact of malicious traffic.

• Rate limiting: Controls the number of requests allowed from a single IP, reducing the effect of volumetric attacks.
• Traffic shaping: Prioritizes legitimate traffic and deprioritizes or drops suspected attack traffic.

Example: When a botnet launches a DDoS attack, flooding the network with traffic, the firewall identifies the surge in requests and filters out traffic from malicious IPs, ensuring that legitimate users still have access.

4) Enhancing VPN security for remote access

Firewalls play a key role in securing virtual private networks (VPNs) used by remote workers. They enforce strong encryption, user authentication, and access controls to ensure that only authorized users can connect to the internal network.

• IPSec and SSL VPNs: Firewalls support secure VPN protocols, providing encrypted tunnels for data transmission.
• Multi-factor authentication: Requires additional verification steps, reducing the risk of compromised credentials.

Example: An employee attempts to connect to the company network from an untrusted device. The firewall denies access based on policy settings that restrict VPN connections from unknown devices, preventing a potential breach.

Strengthen your network firewall security with ManageEngine EventLog Analyzer

Securing your network with firewalls is essential, but effective firewall log analysis and monitoring are what truly help detect threats and ensure compliance. ManageEngine EventLog Analyzer is a comprehensive log management solution for analyzing firewall logs, identifying suspicious activities, and gaining actionable insights across your network. It offers extensive, out-of-the-box reports for a wide variety of firewall providers, like Cisco , Fortinet, Palo Alto Networks, Sophos, SonicWall, and many more.

With support for logs from these industry-leading firewall vendors, EventLog Analyzer helps you make sense of the vast amounts of log data generated, delivering insights with predefined and customizable reports such as:

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• Firewall allowed traffic: Gain visibility into traffic permitted by the firewall, including details on source and destination IPs, protocols used, and traffic patterns. This helps you understand normal traffic flow and detect any anomalies.

• Firewall denied traffic: Identify and investigate denied traffic to uncover potential unauthorized access attempts, blocked IP addresses, or network scanning activities.

• Logons and failed logon: Track successful and failed logon attempts across your network. Failed logon attempts can be a sign of brute-force attacks or compromised accounts.

• Firewall account management: Monitor changes made to user accounts on the firewall, such as new account creation, account deletions, and permission changes, helping you detect unauthorized changes.

• Firewall policy management: Stay on top of changes made to your firewall policies and rules. Unauthorized policy changes can introduce vulnerabilities, and this report helps ensure that only approved modifications are made.

• Firewall IDS or IPS: Analyze data from the firewall’s IDS or IPS to identify and respond to intrusion attempts quickly.

• Firewall security: Get a holistic view of your firewall’s security status, including potential threats, blocked IP addresses, and unusual traffic patterns.

Beyond just reporting, EventLog Analyzer’s predefined, real-time alerts ensure you’re notified immediately about critical incidents like unauthorized policy changes or repeated login failures, helping you act before an incident escalates.

The platform’s log correlation capabilities also add an extra layer of security by identifying patterns across logs from multiple devices. For instance, if there’s a surge in outbound traffic on a Juniper firewall followed by changes in user permissions on a FortiGate device, the correlation engine can flag this as a potential data exfiltration attempt.

FAQ on network firewall security

What is network firewall security?

Network firewall security involves using firewalls to control and monitor network traffic based on security rules, protecting against unauthorized access and cyberthreats.

How does a firewall improve network security?

A firewall improves network security by filtering traffic, enforcing access controls, blocking malicious traffic, and monitoring for suspicious activities.

Can a firewall protect against all cyberthreats?

While firewalls provide strong protection against many threats, they should be used in combination with other security tools, like antivirus software, IDSs and SIEM solutions, for comprehensive security.

What is the difference between a hardware firewall and a software firewall?

A hardware firewall is a physical device that sits between your network and the internet, while a software firewall is installed on individual devices. Both types filter traffic but serve different needs based on the environment.

How often should firewall rules be updated?

Firewall rules should be reviewed and updated regularly, especially after network changes, to ensure they remain effective against current threats.

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