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Denial of Service - DoS

DoS stands for "Denial of Service" and refers to a type of cyberattack where an attacker attempts to render a service, resource, or infrastructure inaccessible or non-functional by disrupting or interrupting normal operation. The main goal of a DoS attack is to deny legitimate users access to a service or resource by impairing the availability of the service.

There are various types of DoS attacks, including:

  1. Volumetric Attacks: These attacks overwhelm the target with a large volume of traffic or requests to exhaust its resources and make it unreachable. An example of a volumetric DoS attack is a Distributed Denial of Service (DDoS) attack, where attackers use a multitude of compromised devices to simultaneously flood the target with traffic.

  2. Protocol Flood Attacks: These attacks exploit vulnerabilities in network protocols to overwhelm the target's resources. An example is a SYN Flood attack, where the attacker sends a large number of TCP SYN requests without responding to them, causing the target to exhaust resources processing these requests.

  3. Application Layer Attacks: These attacks target vulnerabilities in applications or services, attempting to crash or overload them by sending specially crafted requests or payloads. An example is an HTTP Flood attack, where the attacker sends a large number of HTTP requests to a website to exhaust its resources.

The impact of DoS attacks can be significant, including service outages, disruption of business operations, financial losses, and reputational damage. Organizations implement various measures to protect against DoS attacks, including the deployment of firewalls, Intrusion Detection and Prevention Systems (IDS/IPS), load balancers, Content Delivery Networks (CDNs), and specialized DoS protection services.

 


XML External Entity Injection - XEE

XML External Entity (XXE)-Injection is a type of attack targeting XML processing vulnerabilities in applications. In an XXE attack, an attacker attempts to introduce malicious external entities into XML documents and persuade the application to process these entities. This can lead to security issues, including theft of sensitive data, remote code execution, or denial of services.

Here's a basic explanation of how an XXE attack works:

  1. An attacker manipulates an XML document being processed by the targeted application by inserting malicious external entities into the document. An external entity is a reference to an external resource typically defined in a Document Type Definition (DTD) or XML Schema.

  2. The attacker attempts to coax the application into processing the malicious external entities, for example, by sending a specially crafted HTTP request or XML data to the application.

  3. When the application processes the malicious external entities, it can have various effects, including accessing sensitive files or data on the server, executing remote code, or denying services.

A typical example of an XXE attack is stealing sensitive files, such as the contents of configuration files or password files on the server. Through clever manipulation of the XML document, an attacker can persuade the application to disclose the contents of these files.

To protect against XXE attacks, developers need to carefully examine how XML data is processed in their applications. They should ensure they use secure XML parsers, disable external entities, avoid using XML data directly in conjunction with confidential files or data, and thoroughly validate and filter incoming XML data to remove unwanted entities. Enabling XML schema validation and using Content Security Policies can also help prevent XXE attacks. It's also important for administrators to regularly audit their systems and applications for known XXE vulnerabilities and install security updates to minimize potential attack vectors.

 


Hypertext Transfer Protocol Secure - HTTPS

HTTPS stands for "Hypertext Transfer Protocol Secure." It is an encrypted version of the HTTP protocol used for transmitting data over the internet. HTTPS establishes a secure connection between a web browser and a web server by encrypting the data during transmission.

The encryption in HTTPS is provided by SSL (Secure Sockets Layer) or its successor TLS (Transport Layer Security). These protocols enable the encryption of data transmitted between the user's browser and the server, meaning that sensitive information such as usernames, passwords, and credit card details are protected from potential attackers.

Some key features of HTTPS include:

  1. Privacy: By encrypting the transmitted data, HTTPS offers high privacy, ensuring that confidential information is protected from prying eyes.

  2. Authentication: HTTPS ensures that the user is connected to the actual server and not a fake one. This is facilitated by digital certificates issued by trusted certification authorities.

  3. Integrity: HTTPS ensures the integrity of the transmitted data, ensuring that it has not been manipulated during transmission.

HTTPS is used in a variety of applications, especially in e-commerce websites, online banking, social networks, and other services where privacy and security are paramount. It has largely replaced traditional HTTP in many areas as it provides a more secure way to transmit data over the internet.

 


Port

A port is a logical communication endpoint that allows various applications on a computer to send and receive data. In networking technology, a port refers to a number that is assigned to a specific application or service on a computer, used to control traffic to that application or service.

Ports are typically represented by a 16-bit number and can range in value from 0 to 65535. The first 1024 ports are known as well-known ports and are reserved for specific services. For example, port 80 is commonly reserved for HTTP (Hypertext Transfer Protocol) used for web traffic, while port 443 is typically reserved for HTTPS (HTTP Secure) used for encrypted web traffic.

Ports are often used in conjunction with the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP), both of which are protocols in the Internet Protocol suite (TCP/IP). TCP is a connection-oriented protocol suite, while UDP is a connectionless protocol suite. Both protocols use ports to facilitate data communication between different applications.

 


Hypertext Transfer Protocol - HTTP

HTTP stands for Hypertext Transfer Protocol. It is a communication protocol used for exchanging information on the World Wide Web. HTTP facilitates the transfer of text, graphics, sounds, videos, and other files between web browsers and web servers.

In essence, HTTP works by having the web browser send a request to a web server, and the server responds with the requested data. The browser's request is usually specified in the form of a URL (Uniform Resource Locator), and the server replies with the requested content or an error if the request is unsuccessful.

HTTP is a stateless protocol, meaning that each request is considered independent of previous ones. This implies that the server does not store information about prior requests from the same client. To maintain state information between requests, cookies can be used.

It is important to note that there is a more secure version called HTTPS (Hypertext Transfer Protocol Secure), which enables encrypted communication between the web browser and the web server. HTTPS protects the integrity and confidentiality of the transmitted data and is recommended for secure transactions on the internet, such as online payments or transmitting sensitive information.

 


Application Layer - OSI Layer 7

The Application Layer is the topmost layer in the OSI (Open Systems Interconnection) model, encompassing functions directly related to the interaction between the application and the end user. This layer provides services accessible to application software and end-users. The primary tasks of the Application Layer include offering network services, facilitating communication, and transferring data between applications.

Some typical services and protocols used in the Application Layer include:

  1. HTTP (Hypertext Transfer Protocol): Used for exchanging hypertext documents on the World Wide Web.

  2. SMTP (Simple Mail Transfer Protocol): Used for email transmission.

  3. FTP (File Transfer Protocol): Enables file transfer over a network.

  4. DNS (Domain Name System): Provides domain name to IP address translation.

  5. SNMP (Simple Network Management Protocol): Used for network management and monitoring.

The Application Layer serves as an interface between the application and the lower layers of the OSI model. It is responsible for ensuring that applications on different devices can communicate by providing services such as data transfer, error control, and security.

 


Secure WebSocket - wss

Secure WebSocket (wss) is a variant of the WebSocket protocol based on the HTTP Secure (HTTPS) protocol. WebSocket is a communication protocol that enables bidirectional communication between a client and a server over a single, persistent connection. Unlike traditional HTTP connections, which are based on request and response, WebSocket allows continuous real-time data transmission.

The security of WebSocket is ensured by using TLS/SSL (Transport Layer Security/Secure Sockets Layer) for encrypting and authenticating the data transmission. By using wss, the communication between the WebSocket client and server is encrypted, ensuring the confidentiality and integrity of the transmitted data.

The use of wss is particularly important when transmitting sensitive information, as encryption ensures that third parties cannot eavesdrop on or manipulate the data. This is especially relevant when WebSocket is employed in applications such as real-time chats, online games, financial transactions, or other scenarios where privacy and security are of high importance.

 


Websockets

Websockets are an advanced technology for bidirectional communication between a web browser (client) and a web server. Unlike traditional HTTP connections, which typically work in a unidirectional manner (from the client to the server), Websockets enable simultaneous communication in both directions.

Here are some key features of Websockets:

  1. Bidirectional Communication: Websockets allow real-time communication between the client and server, with both parties able to send messages in both directions.

  2. Low Latency: By establishing a persistent connection between the client and server, Websockets reduce latency compared to traditional HTTP requests, where a new connection has to be established for each request.

  3. Efficiency: Websockets reduce overhead compared to HTTP, requiring fewer header details and relying on a single connection instead of establishing a new one for each request.

  4. Support for Various Protocols: Websockets can use different protocols, including the WebSocket protocol itself, as well as Secure WebSocket (wss) for encrypted connections.

  5. Event-Driven Communication: Websockets are well-suited for event-driven applications where real-time updates are required, such as in chat applications, real-time games, or live streaming.

Websockets are widely used in modern web applications to implement real-time functionalities. Using Websockets can make applications faster and more responsive, especially when dealing with dynamic or frequently changing data.

 


Express.js

Express.js is a popular web application framework for Node.js. It facilitates the creation of web applications and APIs by providing a simple, flexible, and powerful structure for routing, handling HTTP requests, and defining endpoints. Express offers numerous features and middleware that allow developers to quickly and efficiently build robust web applications. Its modular nature enables developers to add additional functionality through middleware and plugins, further customizing and extending the application framework.

 


Asynchronous JavaScript and XML - AJAX

Ajax stands for "Asynchronous JavaScript and XML" and is not a standalone technology but rather a collection of web development techniques. Ajax allows web pages to asynchronously exchange data between the web browser and the server without reloading the entire page. This facilitates a faster and smoother user experience, as only the relevant parts of the page need to be updated instead of reloading the entire page.

The key technologies used in Ajax are:

  1. JavaScript: Ajax heavily relies on JavaScript, which is executed in the user's web browser. JavaScript is used to capture events, manipulate the Document Object Model (DOM), and send HTTP requests to the server.

  2. XMLHttpRequest: This JavaScript object is used to send asynchronous requests to the server. It allows the web browser to retrieve data from the server or send data to the server without reloading the entire page.

  3. HTML/CSS: The received data can be dynamically inserted into the DOM structure using JavaScript to update the page. Styling changes can also be applied using CSS to alter the appearance of the page.

While the name "Ajax" suggests XML (Extensible Markup Language), other data formats like JSON (JavaScript Object Notation) are often used today as they are more easily processed by JavaScript.

Ajax gained popularity as web applications became more complex, and users demanded a more responsive user interface without constantly reloading entire pages. Today, Ajax is used in many modern web applications to provide an improved user experience.