What is a Firewall?

A firewall is a security barrier designed to defend computer networks from unauthorized access and potential threats. It acts as a virtual gatekeeper, monitoring incoming and outgoing network traffic, and making decisions based on predefined security rules.

ben kazinik

24.07.2023

8 min read

Firewalls prevent unauthorized users, malware, and cyberattacks from breaching your network by filtering data packets and blocking malicious connections. They play a crucial role in maintaining the integrity and confidentiality of sensitive data, ensuring a safer and more secure digital environment.

How Does a Firewall Work?

A firewall works by establishing a shielding barrier between a computer network and the outside world. It examines incoming and outgoing data packets, analyzing their source, destination, and content against a set of predetermined security rules. 

Based on these rules, the firewall decides whether to allow or block the data packets.

It effectively filters out malicious traffic, unauthorized access attempts, and potential threats, ensuring that only legitimate and safe data can enter or leave the network. By acting as a gatekeeper, the firewall helps to maintain network security, secure sensitive information and prevent cyberattacks. 

Why Are Firewalls Important?

Firewalls are important, since they supercharge your security by:

• Protection Against Unauthorized Access: Firewalls act as a barrier between your internal network and the outside world, preventing unauthorized users and malicious actors from accessing your sensitive data.
• Defense Against Cyber Attacks: Firewalls play a crucial role in defending against various cyber attacks, such as hacking attempts, malware infections, and denial-of-service (DoS) attacks.
• Data Privacy: Firewalls help protect sensitive data, such as personal information and financial records, by ensuring that only authorized users and applications can access it.
• Network Segmentation: Firewalls can be used to segment a network into smaller, more manageable zones. This helps to contain potential security breaches and limit their impact.
• Application Control: Firewalls can control which applications are allowed to access the network and which are not.

With firewalls in place, you can confidently operate online, knowing that your network is fortified against potential security breaches and unauthorized intrusions.

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Common Uses of Firewalls

Firewalls serve various vital purposes in network security, including:

Cyber Threat Defense

Firewalls act as a formidable shield against cyber threats by:

• Continuously monitoring network traffic
• Identifying potential risks
• Blocking malicious content from breaching the system

Logging and Audit Functions

Through detailed logging and auditing, firewalls enable administrators to:

• Analyze network activities
• Track potential security incidents
• Enhance overall network visibility for effective threat response

Traffic Filtering

By inspecting data packets and filtering out suspicious or unauthorized traffic, firewalls help optimize network performance and ensure that only legitimate and safe data is allowed to pass through.

Access Control

Firewalls enforce access policies, determining which users or devices are permitted to access specific resources or services, reducing the risk of unauthorized access to critical information.

Secure Remote Access

Firewalls facilitate secure remote connections, enabling remote employees to access the network and its resources in a protected manner:

• Ensuring data confidentiality and integrity outside the traditional office environment

The Most Common Types of Firewalls

Here are the most common types of firewalls.

By Implementation

There are three ways you can implement a firewall.

• Hardware Firewalls: These are physical devices installed at the network perimeter to control incoming and outgoing traffic. They offer high performance and dedicated security features.
• Software Firewalls: These are applications installed on individual computers or servers to protect them from unauthorized access. They are more flexible and cost-effective than hardware firewalls.
• Cloud Firewalls: These are firewalls delivered as a service over the internet. They are easy to deploy and manage,and they offer scalability and flexibility.

By Filtering Method

There are multiple ways that firewalls can filter traffic, including.

• Packet Filtering Firewalls: These are the simplest type of firewalls that examine the header of each packet and allow or deny it based on a set of rules. They are fast and efficient but not very secure.
• Circuit-Level Gateways: These firewalls operate at the session layer of the OSI model and monitor TCP handshakes to ensure that sessions are legitimate. They are faster than packet filtering firewalls but offer less security.
• Stateful Inspection Firewalls: Stateful firewalls keep track of the state of each connection and use this information to make more informed filtering decisions. They are more secure than packet filtering or circuit-level gateways but can be slower.
• Application-Level Gateways (Proxy Firewalls): These firewalls act as intermediaries between clients and servers,inspecting and filtering traffic at the application layer. They offer the highest level of security but can be complex to configure and manage.
• Next-Generation Firewalls (NGFWs): These firewalls combine the features of traditional firewalls with additional security features, such as intrusion prevention systems (IPS), web application firewalls (WAF), and deep packet inspection (DPI). They offer comprehensive protection but can be expensive.

Components of a Firewall

Firewalls have a wide variety of components, including: 

• Hardware: Own processor running firewall software.
• Software: Applies security controls to incoming data.
• Real-time monitoring: Checks traffic at the firewall’s entrance.
• IP packet filters: Examines data packets for potential threats.
• Proxy servers: Acts as a barrier between your network and the internet.
• VPN: Encrypts and forwards data securely.
• NAT: Changes IP packet addresses for multiple hosts using the same IP.
• SOCKS server: Routes traffic on the client’s behalf for inspection.
• Mail relay services: Inspects email messages for threats.
• Split DNS: Dedicates internal and external network usage to separate servers.
• Logging: Records activity for threat analysis and review.

7 Firewall Best Practices

By following these seven best practices, businesses can bolster their defenses and mitigate potential cyber risks.

#1: Always Update Your Firewalls

Ensures the latest security patches and enhancements are in place, guarding against emerging threats.

#2: Use Antivirus Protection

Provides an additional layer of protection, detecting and neutralizing malware attempting to breach the network.

#3: Leverage a VPN Alongside a Firewall

Enhances data encryption and secure remote access, safeguarding sensitive information from interception.

#4: Block Traffic by Default

Reduces exposure to unauthorized access attempts and potential threats.

#5: Specify Source IP Address, Destination IP Address, and Destination Port

 Adds granular control over network traffic, minimizing vulnerabilities.

#6: Conduct Regular Firewall Audits

Helps identify potential weaknesses or policy violations, enabling prompt corrective actions.

#7: Have a Central Management Tool for Firewalls

Ensures consistent policies across the network and simplifies security management.

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Firewall Vulnerabilities

Despite their robust security features, firewalls are not 100% bulletproof to vulnerabilities. 

Understanding potential weak points can help businesses proactively address these risks and fortify their network defenses against various cyber threats. Some of the weak points of firewalls include:

Insider Attacks

Internal users with malicious intent or unintentional mistakes can bypass firewalls, making insider attacks a critical concern for organizations.

Distributed Denial of Service (DDoS) Attacks

Overwhelming a firewall with massive traffic volumes, DDoS attacks can disrupt network operations and potentially compromise security measures.

Malware

Advanced malware can exploit vulnerabilities in firewalls, enabling unauthorized access and data exfiltration.

Patching/Configuration

Failure to promptly apply security patches or misconfiguration of firewall settings can create openings for cybercriminals to breach the network.

Remote Logins

Weak passwords or improper remote login protocols may provide attackers with unauthorized access to the network through remote access points.

Spam

While not directly targeting firewalls, spam emails can introduce malware and phishing attempts, potentially circumventing network security measures.

The Limitations of a Firewall

Firewalls primarily focus on controlling traffic based on predefined rules, making them susceptible to attacks that disguise themselves within legitimate protocols. They may struggle to detect sophisticated malware or advanced threats, and once inside the network, firewalls cannot prevent lateral movement. 

Plus, encrypted traffic poses a challenge as firewalls have limited visibility into the content, potentially allowing threats to go undetected. 

Despite these limitations, integrating firewalls with other security measures and adopting a multi-layered approach can enhance overall network protection.

The Future of Network Security

The future of network security is witnessing significant shifts in traffic patterns and data center architectures. While firewalls have played a crucial role in securing networks, the rise of east-west traffic and virtualization poses new challenges. 

To address these changes, emerging trends in network security are gaining traction, such as:

Software-defined perimeter (SDP)

Offers lower latency and better identity-centric security, focusing on securing user access rather than IP-based access in virtual and cloud-based architectures.

Secure Access Service Edge (SASE)

Has become increasingly important for safeguarding networks against evolving threats by providing comprehensive security solutions in a cloud-delivered framework.

Firewall as a Service (FWaaS)

Examines remote employees’ and servers’ traffic while offering scalability and flexibility from the cloud through a Firewall as a Service (FWaaS) offering.

Zero-Trust Policy

Assumes potential malicious intent in all access requests, granting access only on an as-needed basis, making it critical for future network security.

Artificial Intelligence (AI) and Automation

Poised to play a significant role in network security, improving threat detection and response capabilities.

Embracing Innovation in Network Security

In conclusion, the future of network security is constantly evolving, driven by changing traffic patterns, virtualization, and emerging threats. 

While traditional firewalls remain vital, new approaches like Software-defined perimeter (SDP), Secure Access Service Edge (SASE), Firewall as a service (FWaaS), zero-trust policies, and artificial intelligence (AI) are gaining prominence. 

By staying ahead of these trends and adopting innovative security measures, organizations can fortify their networks against cyber threats effectively.

To ensure comprehensive protection, consider leveraging Perimeter 81’s Firewall-as-a-Service (FWaaS) solution. 

With its cloud-based Next-Generation Firewalls (NGFWs) and scalable advantages, Perimeter 81 empowers remote employees and secures server connections. Embrace the future of network security today by exploring FWaaS and enhancing your organization’s digital defense.Learn more about Perimeter 81’s Firewall-as-a-Service here.

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