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Understanding Firewalls

Latest reply: Jun 18, 2021 12:58:38 236 19 11 0 0

Hello everyone, Firewalls are the foundation of a defense-in-depth network security strategy. I am going to present you a resume of this useful tool and its types. If any misunderstanding, kindly describe in comments.

• First,they’re designed to protect organizations from network-based attacks.

• Firewalls do this by filtering data packets that go through them.

• They can be a standalone network device or software on a computer system,

meaning network-based (hardware) or host-based (software) “ Windows

defender in our computer it protect as only the computer”.

Types of Firewalls

• Packet Filtering Firewalls

• Circuit-Level Firewalls

• Application-Level Firewalls

• Stateful Multilayer Inspection Firewalls

    1.Packet Filtering Firewalls

        • 1 st generation and most basic type of firewall. , the most unexpensive one.

        • How they works: They inspect all data packets that attempt to traverse it, and based on pre-defined rules,                packets are either allowed or denied.

        • These predefined rules are commonly called an Access Control List (ACL).

        • Now how this rules setup , they setup base on common TCP/IP packet attributes

        • Packet filtering rules are common TCP/IP packet attributes:

                – Source IP Address

                – Destination IP Address

                – IP Protocol – Source TCP/UDP Port

                – Destination TCP/UDP Port

                – Inbound Firewall Network Interface

                – Outbound Firewall Network Interface

    2.Circuit-Level Firewalls

        • Considered 2nd generation firewalls.

        • They operate at the Transport Layer of the OSI Model (Layer 4) and monitor TCP/IP sessions.

        • Instead of analyzing each individual packet, they monitor the TCP handshake.

        • Valid TCP sessions are allowed to pass, while invalid and terminated sessions are not.

        • Hackers can alter the 3-way handshake process attempting to cause denial of service (DoS) attack.

        • If the firewall believes an attack is occurring, it will block the traffic.

    3.Application-Level Firewalls

        •Also known as proxy servers, these firewalls operate at the Application Layer of the OSI Model (Layer 7).

        • Specifically, proxy servers can provide the following services:

        • Filter: Filters packets based on an application or service (FTP, SMTP, etc.).

        • Caching: Provides caching services, for example:

                – When you request a page from a website, the proxy server will retrieve it and then cache

                it in its memory.

                – The next time someone requests that website, the proxy server can retrieve it from its


                – This saves Internet bandwidth.

        • Logging: Has the ability to log user activity for auditing purposes.

   4.Stateful Multilayer Inspection Firewalls

        • Provide the functionality of packet filtering, circuit-level and applicationlevel

        firewalls combined.

        • Can filter traffic at the OSI Network Layer with ACLs.

        • Can filter traffic at the OSI Transport Layer by monitoring TCP sessions.

        • Can also filter traffic at the OSI Application Layer based on an application or

        service (FTP, DNS, HTTP, etc.).

        • They are also the most expensive type of network firewall.

Hope it was helpful , thanks 

  • x
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Created May 9, 2021 16:20:18

Well done
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MVE Created May 9, 2021 16:27:41

Good job
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Created May 9, 2021 16:28:33

Thanks for sharing
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Moderator Created May 9, 2021 22:58:00

You are welcome all
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csk99 Created May 10, 2021 05:17:33 (1) (0)
Admin Created May 10, 2021 01:00:54

Learned more about firewalls,thanks!
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Created May 10, 2021 02:12:54

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Created May 10, 2021 02:52:52

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MVE Created May 10, 2021 05:17:03

Good to know thanks
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Moderator Author Created May 10, 2021 05:52:37

Thanks for the inforamtion
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