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Web Applications

Front End​

  • HTML - Hyper Text Markup Language
  • CSS - Cascading Style Sheets
  • JS - JavaScript

Back End​

  • Database
  • Web Servers
  • Application Servers
  • Web Application Firewall (WAF)

Uniform Resource Locator (URL)​

  • Web address that let's you access the content on the web.

Anatomy of a URL​

  • A URL can contain the following parts

Scheme​

  • Protocol used to access the website.
    • HTTP - Hyper Text Transfer Protocol
    • HTTPS - Hyper Text Transfer Protocol Secure

User​

  • Some websites includes username and password in the format <username>:<password> for authentication.

Host / Domain​

  • Most important part of the URL.
  • It tells the user which website they are accessing.
  • Registering similar misspelt variations of domains for phishing attacks is called Typosquatting.

Port​

  • Port number helps to direct your browser to the right service on the web server.
  • Port numbers range from 1 to 65535.
  • Standard for HTTP is 80 and for HTTPS it is 443.

Path​

  • Path points to the specific file or page on the server.

Query String​

  • Often used to pass data for search terms and form inputs.
  • Query string starts with a question mark (?).
  • Users can modify this data and hence it needs to be handled securely.

Fragment​

  • Points to a specific section of a webpage.
  • Starts with Hash symbol (#).

HTTP Messages​

  • Packets of data exchanged between client and server.
  • Two types of HTTP messages
    • HTTP Request: Sent by user to trigger actions.
    • HTTP response: Sent by server as a response to the request.

HTTP Message Format​

  • Start Line: Tells what kind of message is been sent. i.e. Request or Response.
  • Headers: Key-value pairs with extra information about the HTTP message.
  • Empty Line: Separates header from body.
  • Body: Actual data needed for the message will be stored in the body.