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SQL Injection or SQLi

SQL Injection, often abbreviated as SQLi, is a type of cyber attack that targets databases through the exploitation of vulnerabilities in an application’s software. It is one of the most common techniques used to attack data-driven applications. Here’s an overview:

Definition and Mechanics

• What It Is: SQL Injection is a code injection technique that exploits security vulnerabilities in an application’s software by manipulating SQL queries.
• How It Works: Attackers insert or “inject” malicious SQL code into a query, typically through input fields such as login forms, search boxes, or URL parameters. If the application is not properly secured, this injected SQL code can be executed by the database server, leading to unauthorized data access or manipulation.

Types of SQL Injection

1. In-Band SQLi: The attacker uses the same communication channel to both launch the attack and gather results. This includes:
   • Error-Based SQLi: Exploits error messages from the server to learn about the structure of the database.
   • Union-Based SQLi: Utilizes the UNION SQL operator to combine the results of two or more SELECT statements into a single result.
2. Inferential (Blind) SQLi: The attacker sends data payloads and observes the response of the server to learn about its structure. This type is harder to detect and includes:
   • Boolean-Based Blind SQLi: The SQL query returns a different result depending on whether the query is true or false.
   • Time-Based Blind SQLi: The SQL query forces the database to wait for a specified amount of time before responding, indicating to the attacker whether the query result was true or false.
3. Out-of-Band SQLi: Data is retrieved using a different channel, often used when an attacker is unable to use the same channel for sending the payload and receiving the information.

Impact

• Data Theft: Unauthorized access to sensitive data like usernames, passwords, credit card details.
• Data Loss or Corruption: Deleting or altering records, potentially leading to irreversible damage to the application’s data.
• Loss of Data Integrity: Unauthorized changes to data can compromise its reliability and correctness.
• Compromised System Integrity: In some cases, SQLi can lead to a complete system takeover.

Prevention Measures

1. Input Validation: Ensure all user input is validated for type, length, format, and range.
2. Prepared Statements: Use prepared statements with parameterized queries to ensure the database executes only the code meant to be executed.
3. Stored Procedures: They can encapsulate the SQL code and limit the types of operations that can be performed.
4. Escaping User Input: This is less reliable than prepared statements but involves escaping special characters.
5. Regular Security Testing: Perform security audits and vulnerability testing regularly.
6. Error Handling: Avoid revealing detailed error messages that could give attackers insights into the database structure.
7. Principle of Least Privilege: Limit database user privileges based on the minimum required to perform their function.

SQL Injection is a severe threat due to its potential to compromise sensitive data and disrupt operations. Awareness, proper coding practices, and regular security assessments are key to preventing SQLi attacks.