SQL Injection Attack: The Most Dangerous Attack

• 15 September, 2020
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What Is a SQL Injection Attack?

SQL Injection (SQLi) is one of the most dangerous and common web application hacking techniques. It occurs when an attacker uses malicious SQL queries to manipulate a backend database, allowing them to access data that should not be exposed.

This data often includes sensitive information such as usernames, passwords, personal details, credit card numbers, and confidential business data. A successful SQL injection attack can result in data theft, data loss, unauthorized system access, and even the deletion of entire database tables. In severe cases, attackers may gain administrative control over the affected system.

SQL Injection Tools

Several tools exist that can be used to test web applications for SQL injection vulnerabilities—but these same tools are also commonly used by attackers:

• SQLmap – An open-source penetration testing tool that automates the detection and exploitation of SQL injection flaws
• SQLninja – Focuses on exploiting SQL injection vulnerabilities in Microsoft SQL Server environments
• Havij – A graphical SQL injection tool often used by attackers

Organizations can use tools like SQLmap ethically to assess whether their web applications are properly secured.

SQL Injection Through User Input

SQL injection typically occurs when user input is improperly handled within SQL statements.

SQL Injection Based on 1=1 (Always True)

Consider the following SQL query:

SELECT * FROM Users WHERE UserID = 105 OR 1=1;

Because 1=1 is always true, this query returns all rows from the Users table, bypassing intended restrictions.

SQL Injection Based on ""="" (Always True)

A normal login query might look like this:

SELECT * FROM Users WHERE Name = "Hive" AND Pass = "Password";

If an attacker inputs the following into the username or password field:

• Username: "" OR ""=""
• Password: "" OR ""=""

The resulting SQL query becomes:

SELECT * FROM Users 
WHERE Name = "" OR ""="" AND Pass = "" OR ""="";

This condition always evaluates to true, potentially granting unauthorized access.

SQL Injection Using Batched SQL Statements

Many databases support batched SQL statements, where multiple commands are separated by semicolons. For example:

SELECT * FROM Customers; DROP TABLE Orders;

If successfully executed, this could retrieve customer data and then delete the Orders table—causing severe data loss.

How SQL Injection Works

SQL statements are built using predefined parameters. For example, a login query might be written as:

SELECT * FROM users 
WHERE username = '$username' 
AND password = bcrypt('$password');

Under normal conditions, user input fills in the variables and the query is executed safely.

However, when input validation is weak or missing, attackers can inject malicious SQL code into form fields. This alters the logic of the query, allowing attackers to bypass authentication, extract data, or manipulate the database.

How to Prevent SQL Injection Attacks

To protect against SQL injection vulnerabilities, organizations should adopt the following best practices:

• Regularly test web applications using both static (SAST) and dynamic (DAST) security testing methods
• Use allowlists (whitelists) instead of blocklists (blacklists) when validating user input
• Apply the principle of least privilege to database accounts, ensuring each application component can access only the data it requires
• Use parameterized queries or prepared statements to separate SQL code from user input
• Deploy a Web Application Firewall (WAF) to detect and block SQL injection attempts before they reach the application

SQL injection remains a critical threat due to its simplicity and potential impact. However, with secure coding practices, continuous testing, and layered defenses, organizations can effectively mitigate the risk.