Firewalls come in five primary varieties:
- A basic packet filtering firewall
Verifies each data packet individually.
- Permits or prohibits them according to protocol, port number, or IP address. For instance, “Allow communication from 192.168.1.5 exclusively on port 80.”
- Quick and easy, but not very safe.
How it operates:
• Verifies every packet (data chunk) entering or leaving the system.
• Only examines header data, such as protocol, port number, source IP, and destination IP.
• Uses an Access Control List, a collection of rules, to permit or prohibit traffic.
Example:
A rule could state: Allow IP 192.168.1.10 transmission on port 80 (HTTP); block all other traffic.
Example from real life:
Let’s say your office server only needs to permit web traffic on ports 80 and 443.
In that case, you would write a packet filter rule just for those ports. • Easy and quick, but it’s less secure because it can’t look within the data.
2.Firewall for Stateful Inspection
- More intelligent than packet filtering.
- Monitors current connections and permits only relevant traffic.
- As an illustration, when you visit a website, the response rather than random data is allowed.
- More popular and safe.
How it operates
• Monitors the status of active connections. • Permits packets that are a part of an established, known session. • Prevents anything that doesn’t fit into an established, legitimate link.
Example:
When you go to a website:
- A request (outgoing packet) is sent by your computer.
- The firewall records it and permits the reply (incoming packet).
- Random packets unrelated to your session are banned.
Example from real life: A company’s firewall permits workers to access the internet, but it prevents hackers from attempting to send arbitrary data packets into the network. Because it recognizes ongoing connections, it is more secure than packet filtering.
3.Application-Level Gateway (Proxy Firewall)
- Operates at the application layer. Serves as a go between for users and the
internet.
- Filters material and conceal your actual IP address.
- Effective for email and web security.
How it operates
• Serves as a go-between for users and the internet. • The proxy connects to the destination server on behalf of the user after the user
connects to the proxy. • Examines data at the application layer (such as SMTP, FTP, and HTTP). Example:
• The proxy receives your request first when you visit a website.
• After verifying that request is secure, proxy delivers it to website and returns result to you.
Example from real life:
To prevent access to adult or social media websites while permitting educational
ones, a school employs a proxy firewall. Advantages: Filters particular website material and conceals internal IPs. Cons: Performance is slower.
4.NGFW, or Next-Generation Firewall
A cutting-edge firewall contains intrusion protection, antivirus software, deep packet inspection, and more. Utilized in business settings.
How it operates:
Integrates deep packet inspection (DPI) with stateful inspection.
It has functions such as
- Intrusion Prevention System (IPS).
- Control of Applications.
- Filtering URLs.
- Malware and antivirus scanning.
Example: • It is able to detect and block communication on port 443 that is not typical HTTPS traffic, but rather that of a hacker utilizing a VPN tunnel.
Example from real life:
• Cisco Firepower, FortiGate, and Palo Alto firewalls identify and thwart ransomware assaults and unidentified programs. Utilized by businesses and data centers, it is extremely secure.
5.Firewall-as-a-Service, or Cloud Firewall
o Rather than using a physical device, it is hosted in the cloud. safeguards distant users and cloud-based apps. o  Employed in contemporary networks with cloud connectivity.
How it operates
• Rather than using a local device, it operates on the cloud.
• Safeguards internet-connected branch offices, cloud apps, and remote users. • Overseen by cloud service providers.
Example: • To prevent unwanted access to their servers, a company that uses AWS or Azure
employs a cloud firewall.
Example from real life:
A cloud firewall such as Zscaler or Azure Firewall, is used by a remote business with employees
spread across several cities to safeguard all users’ internet access.