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OSI Model for beginners

Hello aspiring Ethical Hackers. In this blogpost you will learn about the OSI model.  The OSI (Open Systems Interconnection) Model is a theoretical framework for the design and implementation of computer networks. It was developed by the International Organization for Standardization (ISO) and is used as a reference for the design of communication protocols and communication interfaces. As an ethical hacker, you need to have a proper understanding about basic structure of networks and the protocols and frameworks guiding it.  The importance of the OSI Model lies in its ability to provide a common language for the design and implementation of computer networks.

OSI model

In OSI Model, the network is divided into seven layers. These layers from bottom to top are the Physical Layer, Data Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer, and Application Layer. In this article, we will explore each of these layers in more detail.

OSI model for beginners

The OSI model outlines the process of transmitting information from a network device such as a router to its final destination via a physical medium and how the communication with the application is managed. In simpler terms, it establishes a standardized method of communication between various systems. It helps to ensure that communication between different computer systems is possible by breaking down the communication process into seven distinct layers, each with its own set of protocols and functions.

The seven layers of the OSI Model, from bottom to top, are the Physical Layer, Data Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer, and Application Layer. In this article, we will explore each of these layers in more detail.

Layer 1: Physical Layer

The Physical Layer is the first layer of the OSI Model and is concerned with the physical transmission of data between computers. It defines the electrical, mechanical, and functional specifications for the physical connection between devices.

The role of the Physical Layer in networking is to provide a stable and reliable connection between devices by specifying the electrical, mechanical, and functional requirements for data transmission. It also ensures that data is transmitted in a manner that is consistent with the data format defined in the other layers of the OSI Model.

The Physical Layer is responsible for several key functions, including:

  • Establishing and maintaining a physical connection between devices
  • Defining the electrical and mechanical specifications for data transmission
  • Encoding and decoding data for transmission
  • Defining the physical characteristics of the transmission medium

Some examples of Physical Layer technologies include Ethernet, Wi-Fi, and Bluetooth.

Layer 2: Data Link Layer

The Data Link Layer is the second layer of the OSI Model and is concerned with the delivery of data frames between computers. It provides error detection and correction functions and defines the format of the data frames that are transmitted between devices.

The role of the Data Link Layer in networking is to provide reliable data transmission by ensuring that data frames are delivered to the destination device in a timely and accurate manner. It also provides error detection and correction functions, which help to ensure the accuracy of the data that is transmitted.

The Data Link Layer is responsible for several key functions, including:

  • Defining the format of the data frames that are transmitted between devices
  • Error detection and correction
  • Flow control and media access control
  • Media-independent transmission of data frames

Layer 3: Network Layer

The Network Layer is the third layer of the OSI Model and is concerned with the routing of data between computer networks. It provides the means for transmitting data from one network to another and ensures that data is delivered to its intended destination.

The role of the Network Layer in networking is to provide an efficient and reliable means of transmitting data between computer networks. It also ensures that data is delivered to its intended destination by routing it through the network in an efficient and effective manner.

The Network Layer is responsible for several key functions, including:

  • Routing data between computer networks
  • Providing end-to-end connectivity between devices
  • Encapsulating data for transmission between networks
  • Ensuring the reliability and efficiency of data transmission

Some examples of Network Layer technologies include IP (Internet Protocol) and ICMP (Internet Control Message Protocol).

Layer 4: Transport Layer

The Transport Layer is the fourth layer of the OSI (Open Systems Interconnection) Model and is responsible for reliable data transfer between end systems. It is the layer that divides data into manageable segments and ensures that each segment reaches its destination without any errors or lost data.

The Transport Layer is critical to the functioning of a network as it ensures the reliability of data transmission. It does this by dividing data into segments, which are then transmitted and reassembled at the destination end. This layer also provides flow control, which prevents the sender from overwhelming the receiver, and error control, which detects and corrects any errors that may occur during transmission.

The Transport Layer performs several key functions, including:

  • Segmentation: The Transport Layer divides data into segments for transmission.
  • Flow Control: This function ensures that data is transmitted at a rate that the receiver can handle.
  • Error Control: The Transport Layer checks for errors in the data and ensures that any errors are corrected.
  • End-to-End Connectivity: The Transport Layer provides end-to-end connectivity between applications running on different end systems.

There are two main types of Transport Layer protocols:

  • TCP (Transmission Control Protocol): This is a reliable, connection-oriented protocol that ensures that data is transmitted accurately and completely.
  • UDP (User Datagram Protocol): This is an unreliable, connectionless protocol that does not guarantee the delivery or accuracy of data. It is used for applications that do not require reliable data transmission, such as video streaming.

Layer 5: Session Layer

The Session Layer is the fifth layer of the OSI Model and is responsible for establishing, managing, and terminating communication sessions between applications. A session is a continuous exchange of information between two applications and can involve multiple data transfers.

The Session Layer provides a framework for applications to communicate with each other. It coordinates the communication process between the applications and ensures that the data is transmitted in an orderly and synchronized manner. The Session Layer also ensures that the communication between the applications is maintained until it is terminated by either the sender or the receiver.

The Session Layer performs several key functions, including:

  • Session Establishment: The Session Layer establishes a communication session between two applications.
  • Session Management: The Session Layer manages the communication session by maintaining the synchronization of data transfer.
  • Session Termination: The Session Layer terminates the communication session when it is no longer needed.

There are several Session Layer protocols, including:

  • NFS (Network File System): This is a popular protocol for sharing files over a network.
  • RDP (Remote Desktop Protocol): This is a protocol for remote access to a desktop.
  • SSH (Secure Shell): This is a protocol for secure remote access to a computer.

Layer 6: Presentation Layer

The Presentation Layer is the sixth layer of the OSI Model and is responsible for providing a common format for data exchange between applications. The Presentation Layer is responsible for converting data from the Application Layer into a standardized format that can be understood by both the sender and receiver.

The Presentation Layer is responsible for data representation and encryption/decryption of data. It ensures that the data transmitted between applications is in a standard format and can be understood by both the sender and receiver. The Presentation Layer also provides a means for data compression and decompression to reduce the amount of data transmitted over the network.

The Presentation Layer performs several key functions, including:

  • Data Conversion: The Presentation Layer converts data from the Application Layer into a standard format that can be understood by both the sender and receiver.
  • Data Compression/Decompression: The Presentation Layer can compress data to reduce its size for transmission over the network and decompress it for use by the recipient.
  • Data Encryption/Decryption: The Presentation Layer can encrypt data for transmission over the network and decrypt it for use by the recipient.

There are several Presentation Layer protocols, including:

  • MIME (Multipurpose Internet Mail Extensions): This is a protocol for the representation of multimedia content.
  • SSL (Secure Sockets Layer) and TLS (Transport Layer Security): These are protocols for securing data transmission over the internet.

Layer 7: Application Layer

The Application Layer is the top layer of the OSI Model and is responsible for providing a user interface for network applications. It is the interface between the network and the user, allowing applications to request and receive network services.

The Application Layer is responsible for providing network services to applications. It is the interface between the network and the user, allowing applications to request and receive network services. The Application Layer provides a means for applications to interact with the network and access the services provided by the lower layers of the OSI Model.

The Application Layer performs several key functions, including:

  • Network Services: The Application Layer provides network services to applications, including file transfer, email, and other network-based applications.
  • User Interface: The Application Layer provides a user interface for network applications, allowing the user to interact with the network.
  • Network Resource Access: The Application Layer provides a means for applications to access network resources, such as databases or file servers.

There are several Application Layer protocols, including:

  • HTTP (Hypertext Transfer Protocol): This is the primary protocol used for web browsing and web application access.
  • FTP (File Transfer Protocol): This is a protocol for transferring files between systems.
  • SMTP (Simple Mail Transfer Protocol): This is a protocol for sending email.

In conclusion, the Application Layer is the top layer of the OSI Model and is responsible for providing network services to applications. Its functions of network services, user interface, and network resource access provide a means for applications to interact with the network and access the services provided by the lower layers of the OSI Model. The Application Layer is crucial for the operation of network-based applications and services.

The OSI Model in Real-World Networking

The OSI Model is widely used in real-world networking, as it provides a standardized framework for understanding and designing networks.

This model is used in a wide variety of applications, including:

1. Network Design:

The OSI Model is used as a reference for network design, helping network engineers to understand the various components and protocols involved in a network.

2. Network Troubleshooting:

The OSI Model provides a standardized framework for troubleshooting network problems, making it easier for network technicians to diagnose and resolve issues.

3. Network Optimization:

The OSI Model is used to optimize network performance by helping network engineers to identify bottlenecks and other performance issues.

4. Importance of understanding the OSI Model for network technicians:

Understanding the OSI Model is critical for network technicians, as it provides a standardized framework for network design and troubleshooting. Network technicians who understand the OSI Model are better equipped to diagnose and resolve network problems, as well as to design and optimize network performance.

Advantages of OSI Model

There are several advantages to using the OSI Model for network design and troubleshooting, including:

Standardization: The OSI Model provides a standardized framework for network design, making it easier for network engineers to understand the various components and protocols involved in a network.

Modularity: The OSI Model is modular in design, making it easier for network engineers to understand the different layers and protocols involved in a network.

Troubleshooting: The OSI Model provides a standardized framework for troubleshooting network problems, making it easier for network technicians to diagnose and resolve issues.

Understanding the OSI Model is essential for anyone working in the field of computer networking. This standardized framework provides a means of understanding and designing networks, as well as diagnosing and resolving network problems. Network technicians who understand the OSI Model are better equipped to optimize network performance and provide network services to users.

In conclusion, the OSI Model is a critical component of computer networking, providing a standardized framework for understanding and designing networks. Network technicians who understand the OSI Model are better equipped to diagnose and resolve network problems, as well as to design and optimize network performance.

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Whois Footprinting for beginners

Hello aspiring Ethical Hackers. In this blogpost you will learn about Whois Footprinting. In our previous blogpost, you were given an introduction to Footprinting and types of Footprinting. Whois Footprinting is one type of footprinting. In my opinion, Whois footprinting is the first method of footprinting that should be used while starting information gathering.

What is Whois?

Whois is actually a protocol running on port 43. When you or any organization register a domain (eg: hackercoolmagazine.com), a record is created. This record is known as Whois record and is created by an organization called Internet Corporation for Assigned Names and Numbers (ICANN) which regulates domain name registration and ownership. Whois records are maintained by Regional Internet Registries (RIR’s). At present, there are five RTR’s allocated to particular regions.

  1. American Registry for Internet Numbers (ARIN)
  2. African Network Information Center (AFRINIC)
  3. Asia Pacific Network Information Center (APNIC)
  4. Reseaux IP Europeens Network Coordination Centre (RIPE)
  5. Latin American and Caribbean Network Information Center (LACNIC)

What information does Whois reveal?

Whois Lookup reveals information like the owner of the domain, contact details of domain owners, IP address network range used by the organization, domain name server and when a domain has been created and the date of its expiry.

How does it help in Pentesting?

Any business or organization has a website nowadays for which they have to register a domain (person or entity who registers a domain is known as a registrant, while a company registering the domain is known as registrar). So performing Whois Lookup can give anyone information about the domain which can be further used in footprinting.

Types of Whois Lookup

There are two types of Whois Lookup: Thin Whois and Thick Whois.

  1. Thin Whois: Thin Whois Lookup gives only the name of the whois server of the registrar of the domain.   
  2. Thick Whois: Thick Whois Lookup reveals complete information from all the registries for a particular domain.

Kali Linux has a default tool for whois lookup named “whois”. This is how to use it.

Given below are some other Whois Lookup tools.

  1. Whois Lookup (https://www.whois.com)
  2. ICANN Whois (https://whois.icann.org)
  3. MxToolBox (https://www.whois.com/whois/)
  4. Domain Tools (https://whois.domaintools.com)
  5. Who.is (https://who.is/)
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Footprinting guide for beginners

Hello aspiring Ethical Hackers. In this blogpost you will learn about Footprinting or Reconnaissance. It is the first step of Ethical hacking. Although boring a bit, it is one of the most important stages of Ethical Hacking. This is because this stage lays the road to success or failure of the hack as it gives much needed information about the target system or organization.

Objectives Of Footprinting

In Reconnaissance, you gather as much information about the target organization that is useful in gaining access or to learn about the security posture of your organization depending on which color HAT you want to wear. Reconnaissance allows pen testers to reduce the area they need to focus, identify vulnerabilities and finally know about the security posture of the company.

What information does Reconnaissance reveal?

The following information can be collected from the Reconnaissance stage.

  1. Target organization’s network information including domains and sub-domains used by the organization.
  2. Blocks of IP addresses used by the organization that are accessible from outside. etc.
  3. Information about operating systems used by the web server OS, location of the Web server and in some cases user credentials.
  4. Information about the organization like the details of their employees, which include their names, addresses, Phone number, Personal email addresses etc

Types Of Footprinting

types of footprinting

There are two types of footprinting: Passive and Active.

1. Passive Footprinting:

In passive reconnaissance, information about the target organization is collected without actively without engaging with or any interaction with the target organization. This type of foot printing is very difficult as all the information needs to be collected from publicly available resources with search engines, job sites, social media, documents available in public domain etc. On the plus side, this type of foot printing allows pen testers to stay a bit confidential as it raises less suspicions on the target side.

2. Active Footprinting:

In Active reconnaissance, the attackers engage or interact with the target organization. This is simpler than passive reconnaissance as pen testers gets information directly from the target. On the flip side, the security guys at the target organization may already know your intent as it raises suspicions. Information will be collected about the target organization by scanning and enumerating target directly.

Techniques of Footprinting

The various techniques of Reconnaissance include,

Reconnaissance through Search Engines
Reconnaissance through Web Services
Website Footprinting
Email Footprinting
WhoIs Footprinting
DNS Footprinting
Network Reconnaissance
Metadata
Competitive Intelligence
Social Engineering Reconnaissance

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Cross Site Scripting (XSS) for Beginners

Hello aspiring Ethical Hackers. In this blogpost, you will learn about Cross Site Scripting (XSS). Cross-Site Scripting (XSS) attacks are one of the most common web application security threats today. These attacks can allow attackers to steal sensitive data, gain unauthorized access to systems, and compromise entire networks. In this blog post, we will explore what XSS attacks are, their different types, and how to prevent them. In this article, we’ll discuss what Cross Site Scripting is, how it works, types of attacks, how to prevent and detect XSS.

What is Cross Site Scripting?

Cross-Site Scripting (XSS) is a type of security vulnerability that allows attackers to inject malicious code into web pages viewed by other users. The malicious code is typically written in client-side scripting languages like JavaScript, which is executed by the victim’s web browser when they view the infected page. The injected code can then be used to steal sensitive data, such as login credentials or credit card information, or to launch more advanced attacks, such as session hijacking or malware installation.

How XSS Works?

Cross Site Scripting

Types Of XSS

There are three primary types of XSS attacks: Stored (Persistent) XSS, Reflected (Non-persistent) XSS, and DOM-Based XSS. Let’s take a closer look at each type.

1. Stored (Persistent) XSS:

Stored XSS attacks are a type of XSS attack where the malicious code is injected into a website’s database, and then retrieved and executed by other users who view the infected page. This type of attack is particularly dangerous because the malicious code can be stored on the website for an extended period of time and can infect multiple users.

Cross Site Scripting

A typical example of a Stored XSS attack is when a user posts a message on a forum or blog containing malicious code. The code is then stored in the website’s database and is displayed to all subsequent visitors to the page, potentially compromising their systems.

2. Reflected (Non-persistent) XSS:

Reflected XSS attacks are a type of XSS attack where the malicious code is injected into a website’s search field, comment box, or other input field, and then reflected back to the user in the website’s response. This type of attack relies on the user clicking on a link containing the injected code, which then executes the malicious script in their browser.

A common example of Reflected XSS is when an attacker sends a phishing email with a link containing the injected code to a victim. When the victim clicks on the link, the code is reflected back to them through the website’s response and executed in their browser, potentially compromising their system.

3. DOM-Based XSS:

DOM-Based XSS is a type of XSS attack where the malicious code is injected into a website’s Document Object Model (DOM) rather than the server’s response. The injected code is then executed by the victim’s browser when the infected page is loaded.

Real World Examples Of XSS

Here are some of the SQL injection vulnerabilities and their exploitation cases in Real World.

1. British Airways:

In 2018, British Airways suffered a data breach due to cross site scripting. Magecart, a hacker group known for its card skimming scripture exploited a cross-site scripting vulnerability in Java script library known as feedify. This Java script library was modified to record customer data and send it to server controlled by Attackers using this, the attackers collected over 3,80,000 credit card details.

2. eBay:

eBay had a XSS vulnerability in its code for a short time at the end of 2015. EBay used an “URL” parameter to redirect users to the right page. However, the value submitted to this url parameter was not validated before it got inserted into the webpage. In the right attacker’s hand this could allow attacker to inject malicious code into the webpage. Luckily this didn’t happen.

Mitigation and Prevention

Preventing XSS attacks involves a range of technical measures and best practices. Some of the most effective strategies include:

1. Input Validation:

One of the most critical measures for preventing XSS attacks is input validation. This involves filtering and sanitizing user input to ensure that only safe and expected characters are allowed. This can be accomplished using a range of methods, including regular expressions, input masks, and whitelisting.

2. Output Encoding:

Another critical measure for preventing XSS attacks is output encoding. This involves encoding all output from the web application to prevent malicious code from being injected into the page. This can be accomplished using a range of methods, including HTML encoding, URL encoding, and JavaScript encoding.

3. Content Security Policy (CSP):

Content Security Policy (CSP) is a security standard that allows developers to define the sources of content that are allowed to be loaded by their web application. By defining a CSP, developers can prevent malicious scripts from executing on their web pages, thereby mitigating the risk of XSS attacks. CSP works by specifying a whitelist of trusted sources for content, such as scripts, stylesheets, and images. Any content that is not from a trusted source is blocked by the browser, preventing it from executing on the page.

4. Limiting the Use of Client-Side Scripting:

Another effective measure for preventing XSS attacks is to limit the use of client-side scripting languages like JavaScript. This can be accomplished by using server-side scripting languages like PHP or ASP.NET to generate dynamic content. By limiting the use of client-side scripting, developers can reduce the attack surface of their web application and minimize the risk of XSS attacks.

5. Using HTTP-only Cookies:

HTTP-only cookies are a type of cookie that prevents client-side scripting languages like JavaScript from accessing them. By using HTTP-only cookies, developers can protect sensitive information stored in cookies from being accessed by attackers through XSS attacks. This can help prevent session hijacking and other types of attacks that rely on stealing session cookies.

6. Keeping Software Up-to-Date:

Finally, it’s essential to keep all software used by the web application up-to-date, including web servers, frameworks, and third-party libraries. Developers should regularly check for security updates and patches and apply them promptly to reduce the risk of XSS attacks.

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SQL Injection for beginners

Hello, aspiring Ethical Hackers. In this blogpost, you will learn about SQL injection. This vulnerability can result in unauthorized access to sensitive data, modification or deletion of data, and even complete control over the web application and underlying server. (Where is this data stored? In a database. Read what is a database). In this article, you will learn what SQL injection is, how it works, types of attacks, how to prevent and detect this vulnerability.

What is SQL Injection?

SQL (Structured Query Language) Injection is a type of security vulnerability that allows an attacker to manipulate a web application’s database through malicious SQL statements.

How does it work?

These attacks typically occur when a web application does not properly validate user input, such as form data or user-generated content. An attacker can exploit this vulnerability by injecting malicious SQL statements into the input field, which are then executed by the web application’s database.

Sql Injection for beginners

For example, suppose a web application has a login form that accepts a username and password. If the application does not properly validate the input, an attacker could enter a malicious SQL statement into the username field, such as:

Vbnet ‘ OR 1=1–

This statement would trick the web application into believing that the attacker has a valid username, bypassing the need for a password. The double dash at the end of the statement serves as a comment delimiter which ignores any subsequent characters in the query. As a result, the attacker gains unauthorized access to the application and potentially sensitive data.

SQL Injection attacks can also occur through other input fields, such as search boxes, comment forms and URLs. An attacker can use a variety of techniques to inject malicious SQL statements, such as union queries, stacked queries, and blind injection.

Types Of SQL Injection

There are several types of Injection attacks that an attacker can use to compromise a web application. These include:

1. Classic Injection:

This injection type is the most common type, where an attacker injects a malicious SQL statement into an input field to gain unauthorized access to the application and database.

SQL injection

2. Error Based Injection:

This type of Injection attack uses error messages returned by the database to extract sensitive information, such as usernames and passwords.

sql injection

3. Blind Injection:

In a blind Injection attack, an attacker injects a malicious SQL statement into an input field, but does not receive any error messages or output. This makes it difficult to detect the attack and extract sensitive information.

SQL injection
SQL injection

3. Out-Of-Band Injection:

This type of injection attack uses a separate channel, such as DNS or HTTP requests, to extract sensitive information from the database.

5. Time-Based Injection:

In a time-based injection attack, an attacker injects a malicious SQL statement into an input field that causes a delay in the database response time. This delay can be used to extract sensitive information from the database.

Methods Of SQL Injection

SQL Injection attackers use a variety of methods to exploit vulnerabilities in web applications. Some common methods include:

1. Union-Based Injection:

This method involves adding a UNION statement to a SQL query to combine data from multiple tables or queries. This can be used to extract sensitive information from the database.

2. Error-Based Injection:

This method involves triggering a SQL error and using the resulting error message to gain access to sensitive information.

3. Boolean-Based Injection:

This method involves using true or false statements to determine whether certain conditions are met, such as whether a username and password combination is valid.

4. Time-Based Injection:

This method involves using time delays in SQL queries to determine whether certain conditions are met, such as whether a username and password combination is valid.

Real World Examples Of SQL Injection

Here are some of the SQL injection vulnerabilities and their exploitation cases in Real World.

1. Freepik Data Breach:

In year 2022, hackers stole over 8.3million Freepik & Flaticon users by exploiting a SQL injection vulnerability in company Flaticon website.

2. Tesla Motors:

In 2014, a security researcher found a blind injection vulnerability in the Tesla Motors Design studio tool. This vulnerability if exploited could have given anyone access to Tesla backend database including call customer record.

3. Heartland Hack:

A team of hackers exploited an injection vulnerability in Heartland and other company’s website to gain access to their network and plant packet sniffing tools and other malware on their network.

Mitigation and Prevention

To detect and prevent SQL Injection attacks, web application developers and administrators can implement a variety of measures, including:

1. Input Validation:

This involves validating user input to ensure that it conforms to expected patterns or formats. Input validation can be implemented through client-side and server-side validation techniques.

2. Parameterized Queries:

This involves using parameterized queries instead of dynamically generated SQL queries. Parameterized queries use placeholders for user input, rather than incorporating user input directly into the SQL query.

3. Stored Procedures:

Stored procedures are a type of database object that can be called by an application to perform a specific task or set of tasks. They can also be used to prevent this injection attacks by creating parameterized queries that are executed by the stored procedure.

4. Database Hardening:

This involves configuring the database server to restrict user access and ensure that each user has only the necessary access to perform their job functions. It also involves implementing strong passwords and two-factor authentication.

5. Configuring Error Messages:

When a SQL error occurs, the database server may return an error message that includes sensitive information, such as the SQL query that caused the error or details about the database structure. An attacker can use this information to refine their attack and gain further access to the database. To prevent this, it’s important to configure error messages so that they do not reveal sensitive information.

6. Regular Updates:

This involves keeping web applications and database servers up-to-date with the latest security patches and updates.

7. Education and Training:

Regular education and training for developers, administrators, and users is critical to preventing SQL Injection attacks. This includes training on secure coding practices, data security, and password management.

Tools for Detecting SQL Injection

There are several tools available to help detect SQL Injection attacks. Some popular tools include:

1. SQLmap:

This is an open-source tool that automates the process of detecting and exploiting SQL Injection vulnerabilities.

2. Netsparker:

This is a web application security scanner that includes this injection detection and prevention features.

3. Acunetix:

This is another web application security scanner that includes this Injection detection and prevention features.

4. Burp Suite:

This is a web application security testing tool that includes a SQL injection Scanner.

5. OpenVAS:

This is an open-source vulnerability scanner that includes this injection detection and prevention features.

SQL Injection attacks continue to be a major threat to web application security, and the consequences of a successful attack can be devastating. By understanding the methods used by the attackers, and implementing best practices for prevention and detection, web application developers and administrators can effectively protect their applications against this type of attack.