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What is Firewall and How does it Work?

05th Sep, 2023
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    What is Firewall and How does it Work?

    In recent years, the number of transactions conducted online has increased many folds. However, the internet has multiple security vulnerabilities. Hence, the security of our sensitive data has become a major challenge today. Most medium and large organizations with an Internet presence are connected to a network. Creating a partition between the external Internet and the internal network is essential for security. It can be referred to as the "trusted" and the "untrusted" side of the network.

    Various tools and devices exist to help protect our information. Any individual can learn more about these terms by attending the best Cyber Security Certification programs. A firewall, for example, protects our data and prevents unauthorized access. We get you detailed information on firewalls and related topics, such as their function, limitations, and operation in this article.

    What is a Firewall, and What Does a Firewall Do?

    Among the most common security devices are firewalls. A firewall is a security system that filters network traffic and prevents unauthorized access to your network. Firewalls protect your computer from malicious software infections as well as block unwanted traffic.

    Firewall can be configured at various levels of protection. To restrict access to the applications and systems, it uses a set of policies and rules to filter the data and limit the amount of protection needed.

    What is Web Application Firewall?

    In web application firewalls, HTTP traffic between a web application and the Internet is filtered and monitored to protect web applications. Every specific traffic to a resource inside the trusted network and behind the firewall is inspected, analyzed, and allowed to pass or blocked according to predefined security rules. Firewall security rules can be customized and configured.

    Firewall History

    Firewall has been at the forefront of network security for over 30 years and continues to be the most reliable component of defense. The first firewalls dating back to the late 1980s were initially designed as packet filters, which did the job of examining packets, or bytes, sent across a setup of networks between computers.

    Although firewalls that filter packets are still employed today in legacy systems, firewalls have evolved as technology progressed. The essential functions of these firewalls which filtered packets were to ensure the transfer of bytes and packets amongst various systems.

    1. Gen 1 Virus

    In Generation 1, viruses infected stand-alone PCs in the late 1980s, affecting all businesses and propelling the development of anti-virus software.

    2. Gen 2 Networks

    In Generation 2, attacks from the internet affected all businesses, leading to the creation of firewalls. FireWall-1 was the first stateful inspection firewall designed by Check Point CEO Gil Shwed in 1993.

    3. Gen 3 Applications

    During Generation 3, application vulnerabilities were exploited, affecting an increasing number of businesses and driving businesses to introduce Intrusion Prevention Systems Products (IPS).

    4. Gen 4 Payload

    Around 2010, a very new approach was routed in order to implement the firewall. We saw a rise in targeted, obscure, shifty, polymorphic attacks, which impacted most organizations and led to the development of anti-bot and the improvement of sandboxing items.

    The Palo Alto Networks introduced the Next-Generation Firewalls. There are a lot of built-in features and capabilities in these firewalls, such as hybrid cloud support, network threat prevention, application and identity-based control, and scalable performance.

    5. Gen 5 Mega 

    As of 2017, attacks are large-scale, multi-vector, and use advanced attack tools, driving advancements in threat prevention. When it comes to firewalls, network security is the first line of defense. They continue to receive new features as part of continuous development. 

    Twenty-seven years later, firewalls are still the first line of defense against cyberattacks. Due to its increased internet speed, less latency, and high throughput at a lower cost, NetScreen's purpose-built firewall 'Appliance' gained popularity within enterprises around the 2000s. 

    Why Do We Need Firewall in Cyber Security?  

    Firewalls help in preventing malware and viruses. They can also be useful to stop networking-based attacks and application-layers attacks as they behave like a gatekeeper or a barrier preventing such types of attacks and allowing only genuine and filtered data to pass through.

    Unless data packets come or go from a trusted source, they monitor every attempt between our computer and another network. In order to prevent unauthorized access to a private network, we use network firewall software.

    The firewall can be used as a traffic controller on the network that can detect and counter-attack. A firewall can be configured with rules to protect the network and quickly assess and stop any activity which is suspicious from harming the computer.

    The risks of not having a firewall include the following:

    1. Open Access  

    Whenever any system is operating without a firewall, it becomes vulnerable and gives access to all the other networks which basically means that it is open to every kind of connection coming from any source through anyone.

    If a case like this happens, then it becomes difficult to identify threats or any attacks which are being performed on our network. If we are without a firewall, then our devices are open to malicious activities, or any destruction caused on our system.

    2. Lost or Comprised Data

    If we are without a firewall, then we are probably making our devices reachable and accessible by anyone, which means that anyone can have complete control over the network. In this case, cybercriminals can easily delete our data or be used for their personal benefit.

    3. Network Crashes

    If the firewall is absent from your system, then the network can be accessed or shut down by anyone, which may cost us our valuable time and money in order to get our network working again. Therefore, it is extremely essential to use firewalls and secure our network, computer, and data from any unidentified sources.

    How Does Firewall Work?

    A firewall safeguards your PC against harmful data by filtering them out of the system. It protects against backdoors, denial-of-service attacks, macros, remote logins, spam, and viruses. A backdoor is a way to gain access to an application with a vulnerability that attackers exploit to gain access.

    A DoS attack occurs when a hacker requests permission to connect to a server, but when the server responds, it cannot locate the hacker. When this happens repeatedly, the server gets flooded, and it can no longer meet the needs of legitimate visitors. Your network will be protected from DoS attacks if you have firewalls that check connections to ensure they are legitimate.

    Macro scripts are run by applications to automate routine tasks. Malicious macros can be hidden within seemingly innocent data. A firewall can detect malicious macros by examining packets of data. The use of remote logins is often used to assist someone with a computer problem. However, in the wrong hands, they can be used maliciously, especially since remote logins give access to almost all of your computer's functions.

    It is important to not click on anything suspicious in an email, regardless of who the sender appears to be. A firewall can examine all your emails to detect any malwares and prevent your PC from becoming tainted. Spam emails can sometimes contain links to malicious websites. These types of websites activate malicious code which forces cookies onto your computer. These cookies act as backdoors for hackers. Preventing spam attacks is as simple as not clicking on anything suspicious.

    Firewalls inspect data packets for viruses, but antivirus software should be used in conjunction with a firewall to maximize your security. Viruses are capable of erasing data on your computer. Viruses can multiply and then spread to other devices on the network thereby harming them.

    Value of Firewalls in Cybersecurity

    Today's firewalls can be configured with a wide variety of capabilities, such as:

    1. Advanced Network Threat Prevention

    Security becomes more complicated and tedious as cyber-attacks become increasingly evasive, affecting user workflows.

    2. Application Control

    Organizations of all sizes benefit from Application Control, which offers industry-leading application security and identity control. Companies can create flexible policies based on user or group identity to identify, block or limit the usage of applications and widgets.

    Applications are categorized on the basis of a number of criteria, including the type of application, level of security risks, manner in which the resources are used and how the productivity is affected.

    3. Cloud Network Security

    In a public cloud environment, data and assets are now shared between you and the provider. To keep data and assets protected, public cloud network security has to be automated and elastic to keep up with public cloud environments' dynamic needs. 

    4. Scalable Performance  

    The firewall functions as a filter. It compares source and destination IP addresses, protocols, and other information to a ruleset. If properly configured, it will have a "deny all" or "drop all" rule at the end to block anything that doesn't meet the accepted criteria. 

    Different Types of Firewalls in Cyber Security  

    There are basically two types of firewall in network security: Hardware and Software firewall. Hardware firewalls are physical devices and are mounted between your network and gateway. Software firewalls are internal programs on your computer that operate through port numbers and applications.

    Firewall as a Service (FaaS) is also a cloud-based firewall. Just like hardware firewalls, cloud-based firewalls can grow with your organization and provide good perimeter security. There are a few distinct kinds of firewalls in view of their construction and usefulness. Here are the different firewalls you can execute, on the basis of the size of your organization and the degree of safety you really want.

    1. Packet-filtering Firewalls
    Firewall in Cyber Security - Types, Advantages

    A packet-filtering firewall is a type of firewall that can obstruct network traffic IP protocol, a port number, and an IP address. It applies a set of rules which are based on the contents of IP and transport header fields on each packet. Upon receiving and analyzing the outcome, the packet-filtering firewall decides whether to forward or discard the packet.

    This type of firewall is basically meant for networks that are smaller as it is the most basic form of protection. In order to understand this, one must go for the best Ethical Hacking course online with certificate to gain more insight about firewalls.

    As each packet is examined in isolation, packet filters don't have to keep track of any traffic characteristics. This makes them very efficient at determining packet flow. This type of firewall works on the network layer of the OSI model. It is common to run packet-filtering firewall software either on general-purpose computers/routers or on special-purpose routers, and they each have their own advantages and disadvantages. 

    Advantages of Packet-filtering Firewall  

    As most routing devices provide built-in filtering capabilities, there is no need to set up a new firewall device. Packet filtering protects your network from intrusions from computers and networks outside of your local network (LAN). Some of the advantages of packet-filtering firewall include: 

    1. Single router is Needed- In order to protect an entire network from any attacks, only a screening router is required, and this is one of the major advantages of using a packet-filtering firewall. 
    2. Works Faster- With packet filtering routers, packets are accepted and rejected very quickly and efficiently on the basis of destination and source ports and addresses. Whereas on the other hand, other firewalls are very time-consuming as they cannot filter quickly. 
    3. Transparency- In order to use the Packet-filtering firewall, the user does not require any pre-requisite knowledge, nor do they need any cooperation. Until and unless any packets get rejected, the users do not know how the packets are transmitted. In addition, other firewalls require customized software, client machines to be configured, or users to receive specific training. 
    4. Built-in packet Filtering- The capacity of filtering the packets is inbuilt amongst popular hardware and software routing products. 

    Disadvantages of Packet-filtering Firewalls  

    Alongside having several advantages, there are many disadvantages of using a Packet-filtering Firewall: 

    1. Does not Account Context Information- Packet filtering's biggest disadvantage is that it only authenticates IP addresses and port numbers and does not account for context or application information. 
    2. Stateless- Packet filtering has another disadvantage; it lacks memory of previous invasions and filtered packets. Each packet is tested in isolation, and it is stateless, allowing hackers to easily penetrate. 
    3. Does not Protect Against Spoofing- IP spoofing is a method for hackers to intrude into networks by inserting fake IP addresses in packets. Packet filtering does not protect against this method. 
    4. Time-Consuming- Implementing packet filtering firewalls in highly desired filters can be a time-consuming process. Configuring ACLs can also be challenging. 

    2. Proxy Service Firewalls  

    Proxy service firewalls are systems that filter messages at the application layer to improve network security. You can think of it as a middleman between your internal network and outside servers. By analyzing incoming traffic with stateful and deep packet inspection technology, they are more secure than traditional firewalls. 

    3. Stateful Multilayer Inspection (SMLI) Firewalls  

    Stateful Multilayer Inspection firewalls keep track of connections and provide standard firewall capabilities. Traffic is filtered based on state, port, and protocol, as well as administrator-defined rules and contexts. A prior connection and packets from a current connection are used in this process.

    Stateful packet inspection is used by most firewalls to monitor internal traffic. Using multi-layer monitoring, this firewall goes beyond packet filtering. You may need additional software to distinguish between good and bad web traffic.

    4. Unified Threat Management (UTM) Firewalls  

    SMLI firewalls work in conjunction with intrusion prevention and antivirus software to form a unified threat management firewall. UTM may include additional services such as cloud management. 

    Firewall in Cyber Security - Types, Advantages

    5. Next-generation Firewalls (NGFW)  

    Compared to packet-filtering and stateful inspection firewalls, next-generation firewalls are more sophisticated. Unlike standard packet filters, they perform a more thorough inspection of packets, examining not just packet headers but also their contents and sources. As security threats evolve and become more sophisticated, NGFWs are able to block them. 

    6. Network Address Translation (NAT) Firewalls  

    As a result, NAT firewalls are capable of assessing internet traffic and blocking unsolicited communications, so they only accept inbound web traffic from devices on your private network. 

    7. Virtual Firewalls  

    In cloud-based systems, both private and public, virtual firewalls serve as security appliances. Internet traffic is assessed and managed using this type of firewall, whether it is over a physical or virtual network. 

    Key Components of a Firewall  

    A firewall is a collection of hardware and software that, when used together, prevent unauthorized access to a portion of a network. A firewall consists of the following components: 

    1. Hardware  

    Firewall hardware typically consists of a separate computer or device dedicated to running the firewall software functions. 

    2. Software  

    Firewall software provides a variety of applications. In terms of network security, a firewall provides these security controls through a variety of technologies: 

    • Internet Protocol (IP) packet filtering 
    • Network address translation (NAT) services 
    • SOCKS server 
    • Proxy servers for a variety of services such as HTTP, Telnet, FTP, and so forth 
    • Mail relay services 
    • Split Domain Name System (DNS) 
    • Logging 
    • Real-time monitoring 

    Advantages and Disadvantages of Firewall  

    • For the firewall to be effective, it must be capable of handling all possible external threats. 
    • There is a disadvantage to firewalls in which they fail to prevent internal threats, virus attacks and authentic mechanisms used by hackers (such as usernames and passwords). 

    Besides intrusion detection systems and intrusion prevention systems, organizations must implement other mechanisms and controls to protect themselves from these threats. By implementing antivirus and other prevention and detection systems along with firewalls, viruses, trojans, spyware, ransomware, denial-of-service attacks, and malware can be prevented. 

    How to Use Firewall Protection with Examples?  

    For your network and devices to be protected, you need to properly set up and maintain your firewall. To help you secure your firewall, here are some tips: 

    1. Updating Firewalls Often: Keep your firewall up-to-date with firmware patches to prevent any vulnerabilities from being exploited. Generally speaking, personal and home firewall users can update without any problems. However, larger organizations might need to check their configuration and compatibility across their network before updating. Everyone should, however, have processes in place to ensure that updates are made as soon as possible. 
    2. Use Antivirus Protection: Viruses and other infections cannot be stopped by firewalls alone. Security solutions designed to disable and remove these may get past firewall protections. Besides protecting your personal devices, Kaspersky Total Security offers a variety of business security solutions that keep your network clean. 
    3. Limiting Accessible Ports and Hosts with a Whitelist: Inbound traffic is denied by default. Use a whitelist of trusted IP addresses for all inbound and outbound connections. Access privileges should be restricted to the necessities for users. In the event of an incident, it is easier to revoke and mitigate damage if access is enabled when needed. 
    4. Segmented Network: Limiting internal cross-communication can slow down lateral movement by malicious actors. 
    5. Active Network Redundancies to Avoid Downtime: Network hosts and other systems that are important to the operation can be protected from data loss and reduced productivity through data backups.

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    Depending on the functionality, every commercial or application service exposed to the internet will have its own security requirements. In order to implement the most appropriate security control systems, a detailed analysis and feasibility study must be conducted.

    Implementation and continual improvement are the keys to overcoming the world of threats and hackers. KnowledgeHut’s best Cyber Security training provides a good insight of firewalls. To control these external threats, firewalls are among the many solutions available in today's world of cybersecurity.

    Frequently Asked Questions (FAQs)

    1Do you need a firewall at home?

    Yes, because your home network could be opened to every connection without a firewall and you would not be able to detect any incoming threats which can otherwise be blocked on your system. Open access could expose your devices and personal information to malicious access and misuse. 

    2What is a firewall? Explain with an example.

    Firewalls are security devices which filter network traffic and prevent unauthorized access to your network. Firewalls protect your computer from malicious software infections as well as blocking unwanted traffic. They can be configured at various levels of protection.

    3What is the role of a firewall?

    By blocking unsolicited and unwanted incoming network traffic, firewalls can help manage your network traffic and protect your computer and data.

    4What are the 2 main types of firewall?

    The two main types of firewalls are stateful and stateless. Firewalls that monitor and detect traffic patterns and flows on a network are known as stateful firewalls. However, rather than filtering traffic based on rules, stateless firewalls focus only on individual packets. 

    5What is a firewall and its limitations?

    Firewalls are security devices which filter network traffic and prevent unauthorized access to your network. However, because it cannot block access to malicious websites, it is vulnerable to internal threats or attacks as well as to viruses spreading through the internet.


    Mrinal Prakash

    Blog Author

    I am a B.Tech Student who blogs about various topics on cyber security and is specialized in web application security

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