What is a Network Firewall?


Network firewall regulate network traffic based on pre-established security rules, creating a barrier between your trusted internal networks and the untrustworthy external Internet.

Firewalls are intended to keep malware and unauthorised users out of your systems, yet even they cannot stop every potential threat – that’s why additional tools such as endpoint protection and NDR platforms are so vital.


Network firewalls are hardware and software systems designed to create an invisible wall between a private computer or network and untrusted external ones, blocking data packets based on pre-established security rules or allowing them through according to predetermined security rules, thus protecting networks against cyberattacks and threats such as malware or viruses.

Firewalls can be classified by their level on the Open Systems Interconnection model (OSI), which illustrates their operation and interaction with connected systems. Different kinds of firewalls include:

Packet Filtering Firewalls: These firewalls use rules and criteria such as port numbers, IP addresses and packet type to filter data packets based on certain criteria such as port numbers or packet types. Unfortunately they can still be vulnerable to IP spoofing attacks that exploit how packets are transmitted.

Stateful Inspection Firewalls: These firewalls maintain a state table to track new connections made by clients and compares data packets that arrive to this table to see if any match already existing connections; if that occurs, the firewall allows it through without further analysis – an excellent defense against denial-of-service (DoS) attacks which often take advantage of established ones.

Application-level Firewalls: Application-level firewalls analyze payloads of data packets to identify any malicious behavior, such as recognizing unintended commands in Telnet and FTP sessions or any requests that violate established security policies. They can also read and block incoming requests that breach these policies.

Proxy Firewalls: These types of firewalls function similarly to others; however, they serve as an intermediary between clients and servers to prevent direct connections from being made between clients and servers. Proxy firewalls can read and filter multiple application protocols, including Hypertext Transfer Protocol, Domain Name System and File Transfer Protocol.

Next-Generation Firewalls (NGFWs): These firewalls combine traditional capabilities with intrusion prevention systems and advanced threat detection to create comprehensive protection from modern cyberattacks.


Network firewalls serve to safeguard businesses against cyber threats by monitoring data coming in and out, detecting any malicious activity, controlling network traffic based on security rules and protecting against malware attacks that could cause significant harm. They may take the form of physical hardware, software applications or cloud services; corporate networks rely heavily on them as they prevent unauthorized access to confidential data and devices while home networking environments often rely on them as part of PCs or laptops’ operating systems.

Network firewalls work by filtering internet transmissions that belong to businesses through, while only permitting those that belong to specific IP addresses to pass. They analyze all incoming and outgoing connections before making decisions based on pre-established policies set up by IT teams.

As soon as a firewall detects an attempted connection that doesn’t match existing rules, it creates a new rule and evaluates the next packet in its queue – giving rise to potential detection of malicious activities like denial of service (DoS) attacks.

As network threats became more sophisticated, the need for stronger cybersecurity became apparent. Next-generation firewalls (NGFWs) emerged to offer enhanced protection capabilities; these advanced tools combine traditional firewall capabilities with intrusion prevention systems and other cutting-edge technologies in order to stop more advanced cyber-attacks.

NGFWs not only prevent malware from entering a network, but they can also monitor data for anomalies like changes made without authorization to essential files and critical information. This allows businesses to ensure the integrity of their information is not exploited by hackers or malicious insiders.

Newer network firewalls include features to keep up with hybrid work and cloud-dependent operations, including supporting remote workers and managing devices from outside the corporate network. Furthermore, IT teams can deploy one single console network firewall across platforms; additionally smart NGFW tools allow IT departments to segment an organization’s assets by applying internal and external filters – making it easier to develop security policies that suit various users, departments and projects.


Firewalls are essential cybersecurity devices for business networks. They prevent cybercriminals from infiltrating computer systems with harmful content, as well as denial-of-service attacks and SQL injections, among many others. Firewalls come in both software-based and hardware devices forms; depending on the nature of their network, IT teams must choose one which fits best for their organization.

Firewalls have long been part of network security solutions, but their functionality and efficiency continue to evolve and improve with time. Today there are various generations of firewalls which use various forms of filtering methods in order to adapt to evolving threats. Furthermore, different firewalls operate at different levels within OSI (Open System Interconnection).

Some firewalls are tailored specifically to monitor internet transmissions between organizations and outside sources. These packet filtering firewalls – often referred to as packet filtering firewalls – operate under the principle that only traffic originating from authorized IP addresses are admitted into networks, often installed between an organization’s gateway device such as a router or broadband modem.

Stateful inspection firewalls offer an upgrade over simple packet filtering by keeping a log of existing connections and the packets they carry, then using this information to evaluate any future traffic that meets a set of criteria. Furthermore, stateful inspection can identify patterns in both outgoing and incoming packet traffic that occur regularly – for instance recognizing destinations which typically use SSH (secure shell) logins so it can block these by default.

Next Generation Firewall (NGFW), is an advanced network firewall. It offers deeper scanning capabilities such as deep packet inspection and application inspection to block potentially dangerous data packets. Furthermore, threat intelligence feeds may also be utilized to block traffic based on previous behavior of IP addresses or devices sending packets.

While more sophisticated firewalls, NGFWs may still be vulnerable if their patching and configuration is incorrect. Furthermore, because their processes are more intensive than other types, using an NGFW may reduce network connectivity for devices connected to it; as such, IT teams should only deploy them in critical parts of their organization.


Firewalls are an essential element of home network security that ensures only authorized traffic passes through. They monitor outgoing data to prevent it from passing on to another network and can also be configured to block certain files and services using rules set up by IT professionals.

Access Control Lists (ACLs) provide rules to control how packets will be received based on security needs and policies within an organization, with firewalls also capable of determining content type before making decisions on whether they should be allowed or denied access. These ACLs allow rules to be defined based on security needs and policies of an organization while being defined based on ACL rules that define their fate based on acceptance, deletion or rejection based on these lists. These ACLs can also determine what content type should be permitted or denied depending on its ACL rules which allows based on any number of criteria set by ACL rules defined according to ACL rules defined according to ACL rules set by ACL rules defined based on an organizations security needs and policies. Firewalls also assist in this regard by being able to determine its contents which ultimately dictate whether an allow or disallow either packet based on this.

Circuit-level gateways go beyond packet filtering by monitoring TCP handshakes and network protocol session initiation messages to determine whether a connection has been compromised, which allows them to better detect breaches in security. They may also be combined with application layer firewalls for optimal protection.

Network firewalls can protect businesses against both external and internal threats. While hacking and phishing are primary external risks, internal threats often come from employees transferring sensitive data or applications onto unauthorised networks. Firewalls can help limit who can gain access to the system while simultaneously making sure accounts are safe.

A firewall can also be configured to monitor server activity and log any anomalous login attempts or attempts at gaining access. This log helps the admin quickly identify the source of any problems on their servers and resolve them efficiently.

Next-generation firewalls are specifically designed to conduct deep inspection of packets. They can analyze their content to identify which OSI layers it involves as well as detect malware, manage network bandwidth allocation and establish appropriate access controls. They can even be combined with IDS/IPS systems or malware filters for enhanced protection; having these advanced features makes these firewalls more effective than traditional firewalls; however, their complexity increases TCO. To make an informed decision before investing in one.

Mark Funk
Mark Funk is an experienced information security specialist who works with enterprises to mature and improve their enterprise security programs. Previously, he worked as a security news reporter.