SQL Injection (SQLi)

SQL Injection (SQLi) is a type of cyber-attack where an attacker manipulates a web application's database query by injecting malicious SQL code. The goal is to bypass authentication, access or modify data, and in some cases, even gain full control over the server hosting the database.

This type of attack exploits vulnerabilities in an application's software when user input is improperly sanitized or validated before being incorporated into a database query. SQL Injection remains one of the oldest yet most dangerous web vulnerabilities.

Variants

There are several different types of SQL Injection attacks:

• Classic SQLi: Direct injection of malicious SQL code to manipulate the database. Often used to bypass login pages or retrieve sensitive information.
• Blind SQLi: When an application does not display database errors, attackers infer information based on the application's behavior, such as timing differences or error messages.
• Time-Based Blind SQLi: Attackers make the database perform time delays (e.g., SLEEP commands) to deduce information based on response times.
• Error-Based SQLi: Relies on database error messages returned to the user to extract information about the database structure.
• Union-Based SQLi: Uses the UNION SQL operator to combine results from multiple queries, allowing attackers to fetch data from other tables.

Impact

SQL Injection can have devastating effects on organizations. Attackers can steal sensitive customer data like usernames, passwords, and credit card information. They can modify or delete data, cause application downtime, and in severe cases, escalate their access to the entire system. SQLi breaches often lead to financial losses, regulatory fines, and lasting reputational damage.

Discoverability

Discoverability of SQL Injection attacks depends largely on how well the application logs database errors and monitors abnormal activities. Simple attacks might cause visible error messages, making detection easier. However, more sophisticated SQLi, like Blind SQLi, can go undetected without advanced monitoring tools such as Web Application Firewalls (WAFs) and Intrusion Detection Systems (IDS). Regular code audits, penetration testing, and database activity monitoring are key to identifying vulnerabilities before attackers can exploit them.

Types

Authentication Bypass

• Example: By injecting ' OR '1'='1 into a login form, attackers can bypass authentication and gain unauthorized access to restricted areas.

Data Exfiltration

• Example: Using UNION SELECT to retrieve user credentials or other confidential information from the database.

Remote Code Execution

• Example: In certain cases, exploiting SQL Injection vulnerabilities can allow attackers to execute operating system commands, gaining full control over the server.

Destructive Attacks

• Example: Attackers might inject DROP TABLE commands, causing permanent loss of critical data.