Understanding Firewalls: Types and Operational Flow

-An Article by : Akshaya Arunan
-Follow her : Akshaya A. | LinkedIn

⭐ Introduction👇

In the digital age, where data flows freely between networks and devices, safeguarding your digital assets is of paramount importance. This is where firewalls come into play, acting as a crucial defense mechanism in the world of cybersecurity. In this blog, we’ll delve into what firewalls are, explore their different types, and break down their operational flow to help you better understand these network security guardians.

⭐ What is a Firewall ?👇

At its core, a firewall is a security device or software that serves as a barrier between a trusted internal network and an untrusted external network, typically the internet. Its primary purpose is to monitor, filter, and control incoming and outgoing network traffic, ensuring that only authorized and safe data can pass through.

⭐ Types of Firewall👇

1. Packet Filtering Firewalls
Packet filtering firewalls operate at the network layer, where they make decisions based on packet attributes such as source and destination IP addresses, ports, and protocols. They are efficient but lack the ability to inspect the content of packets, which makes them suitable for basic network security.

2. Stateful Inspection Firewalls
Stateful inspection firewalls take network security up a notch. They can not only filter packets based on attributes but also track the state of active connections. This means they make decisions based on the context of the traffic, allowing or denying packets based on the state of the connection.

3. Proxy Firewalls
Proxy firewalls act as intermediaries between the internal network and external servers. They receive requests from internal clients, make the requests to external servers on behalf of the clients, and then return the results to the clients. This approach adds an extra layer of security by hiding the internal network structure.

4. Application Layer Firewalls (Next-Generation Firewalls)
Next-generation firewalls are highly sophisticated. They perform deep packet inspection, allowing them to analyze the content of the traffic and make decisions based on specific applications or services. This advanced level of inspection can identify and block even the most intricate threats.

⭐ Operational Flow of a Firewall👇

Now, let’s take a closer look at how a firewall operates:

Ingress and Egress: Traffic enters and exits the firewall through network interfaces, serving as the entry and exit points for data flow.
Packet Inspection: Each packet is meticulously examined by the firewall, with attributes like source and destination IPs, ports, and protocols scrutinized.
Rule Matching: Predefined rules, often referred to as access control rules or security policies, dictate what actions the firewall should take. For instance, rules can allow web traffic (HTTP) but block specific applications or IP addresses.
Stateful Inspection: Many modern firewalls incorporate stateful inspection. This technology keeps track of active connections, distinguishing between new connection requests, established connections, and related traffic.
Five-Tuple Inspection: Firewalls use a concept called the “ five-tuple ” to identify network traffic based on five key attributes: source IP, source port, destination IP, destination port, and protocol. This granular approach enables precise traffic control and rule enforcement.(Explained in detail below).
Action Decision: Based on rule matching, stateful information, and the five-tuple attributes, the firewall decides what to do with each packet. It can either allow the packet to pass, block it, or in some cases, modify it to meet security criteria.
Logging: Firewalls maintain logs with details about the packets they handle. This information is invaluable for security analysis and troubleshooting.
Proxying and NAT: Some firewalls also perform Network Address Translation (NAT) and act as proxies for specific applications. These additional services enhance security and privacy.
Security Services: Firewalls often integrate with supplementary security services like intrusion detection and prevention systems (IDPS), antivirus, and content filtering, creating a layered approach to security.
Default Policies: In cases where a packet doesn’t match any specific rule, the firewall applies default policies. These policies can either be to deny all traffic by default or to allow all traffic by default, depending on the network’s security strategy.
Alerts and Notifications: When a firewall detects a violation of its rules, it can generate alerts or notifications. These serve as early warnings for administrators to take appropriate actions.

⭐ The 5Tuples in Firewall👇

The “five-tuple” is a fundamental concept in networking and firewall rule management. It consists of five specific attributes that together uniquely identify a network connection or packet. These attributes are:

Source IP Address: This is the IP address of the sender or the origin of the network connection or packet.
Source Port Number: The source port number indicates the specific application or service on the sender’s side that’s sending the data. It helps in identifying which application is generating the traffic.
Destination IP Address: This is the IP address of the receiver or the destination of the network connection or packet.
Destination Port Number: Similar to the source port, the destination port number specifies the application or service on the receiving side that will process the data. It’s crucial for directing the traffic to the correct application.
Protocol: This attribute defines the network protocol being used, such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). The protocol dictates how the data should be handled during transmission.

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Understanding Firewalls: Types and Operational Flow