From zero to hero in bug bounty [Pt. 3]

Recap:

Hi mate! Thanks for joining me on another part of this zero-to-hero bug bounty guide! You're doing an awesome job! Keep going!In part 2 of this guide, I went over common networking terminologies, explained the OSI-Model, briefly introduced you, with simple examples, to what a network was, and much more. If you haven't read it yet, no issue at all, you can access part 2 on my blog. If you did read it, I highly recommend rereading the post again to freshen up your networking knowledge!

In today's issue, I will explain network ports & DNS. I should've added it to the previous part but it got a little lengthy. Long posts can be a bit challenging to follow and I tend to keep this guide simple & easy ;)! Without further ado, let's get started!

Table of Contents:

• Network Ports

• Domain Name System (DNS)

Network Ports:

In the last post, we've seen that a destination IP address is required in order to communicate with another device in the same network. However, to make the connection complete, we need to assign a service port to the IP address as well. Let's take a look at the following example:

As you can see in the illustration above, we had to connect to the host on port 80 (where the HTTP service is actually listening for any incoming connections). And our web browser is listening for a response from the server on the source PORT.Each IP address or device has 65535 network ports. And each one of them can be registered by a running service or program. ICANN has divided this port range into 3 different classes, you do not necessarily need to remember these, but I do recommend you memorize the following common network port numbers and their associated service:

Short summary:The IP address locates the host in the network, while the network port locates the requested service on the host that is connected to the network.

DNS:

Domain Name System (or DNS for short) is responsible for making sure you connect to the correct host whenever you request a domain. You can think of it as a telephone book that converts each number to its associated contact name. Whenever you request a website, the DNS will try to resolve the domain name and get the IP. This means that you do not have to remember IP addresses, but instead, just connect to a domain name. Let's take a look at the following image below:

On your web browser, you request example.com. However, on the backend of this process, the DNS transforms that domain into an IP address to locate the host over the network and successfully make an HTTP connection.This is how DNS works, I do recommend learning more about DNS records (A records, CNAME records, MX records, TXT records, ...) as they will be valuable, especially in the reconnaissance phase!

Thanks for making it this far!

I hope you've enjoyed this post! In the next part, I will explain the HTTP protocol in-depth and move on from there to commonly used tools! Congratulations on making it this far mate! You are one of the few who have done this and you make much more chance to complete this guide and become a bug bounty hunter!

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