How do web applications work? What are the key concepts that you should know, and some tools for automating web requests?

We've grown so accustomed to the internet that we usually access it without thinking twice about how it works, and the myriad systems that enable it.

To understand web security, one must first know (at least at a high level) how the web works.

If you're not already familiar with that, here are some recommended readings to get you started:

• https://developer.mozilla.org/en-US/docs/Learn/Getting_started_with_the_web/How_the_Web_works
• https://developer.mozilla.org/en-US/docs/Learn/Common_questions/How_does_the_Internet_work

Key terms

These are some terms that we will be using fairly often in this course while working with web applications. You will likely already be familiar with them. In case they don't seem familiar, I have included a brief (but non-exhaustive!) explanation of each term.

IP address

This is your address on the internet. Every device connected to the internet has one. Here is an example: 162.199.92.181. You can check out your current IP address by Googling it.

IP addresses come in two flavors: IPv4 and IPv6. Most of the IP addresses you encounter will be IPv4 -- they come in the format a.b.c.d where a, b, c and d are integers in the range [0, 255]. This means that there are 256^4 = (2^8)^4 = 2^32 = 4,294,967,296 possible IPv4 addresses. This was once enough, but the world has been running out of IPv4 addresses for a long time.ww