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Decoding SQL Injection: Strategies for Secure Web Applications

SQL injection has been a persistent plague for web developers since its first discovery over 25 years ago. Despite its longevity, it is still consistently one of the top-rated web vulnerabilities, according to OWASP. While easy to prevent, these simple attacks are also one of the most impactful, putting data integrity at risk for any web application tied to a database. 

What is SQL Injection

A SQL injection attack is a variation of injection attacks where an attacker can trick a web application into passing SQL commands directly to the database on their behalf. This allows attackers to inject toxic SQL queries through data input, granting them the same level of access as the application and enabling them to query and manipulate the database from within. 

While these are considered web application attacks, the actual target of the attacks is the underlying databases that power the website. This places all the data inside the database at risk of being leaked, modified, or eliminated, compromising data security and operations. 

How Does SQL Injection Work?

These attacks capitalize on exploiting vulnerable inputs in web applications. Generally, a web application takes user input via a form. Users are expected to type in data, and then, after clicking a button, the application processes the input. This is not a problem for regular users as the data provided is generally just letters or numbers, which the application has no problem parsing.

The problem emerges when insufficient input validation allows users to insert strings modified to include SQL commands. Unlike regular input, special characters tell the application to stop processing the standard input and start executing the appended command. Sometimes, the resulting query is displayed directly on the screen, yet it can also happen behind the scenes. These cases are referred to as blind SQL injection attacks, and even though they don’t always result in visual responses, the damage can still be significant as they may perform database modifications, allowing attackers to escalate the attack. 

However, it’s important to note that it does not just form fields subject to these attacks. Any means of data input that results in a database interaction, such as URL parameters or direct API calls, can be compromised in this manner if they lack adequate controls to prevent it. 

Examples of SQL Injection Attacks

SQL hacking attacks are not complex, making them a standard component of an attacker’s toolkit. 

It starts with a simple SQL query on the back end, like the one below.

SELECT * FROM products WHERE name LIKE '%$searchTerm%';

In this query, $searchTerm is replaced by the user’s input. Usually, if a user types “phone,” the query executed by the server would be:

SELECT * FROM products WHERE name LIKE '%phone%';

This would return all products containing the word “phone” in their names.

Let’s see how an attacker could exploit this with an SQL injection. Suppose the attacker inputs ‘; DROP TABLE products; –. The resulting query becomes:

SELECT * FROM products WHERE name LIKE '%'; DROP TABLE products; --%'

In this scenario, the injection:

  1. Terminates the Original Query: The ‘; part closes the original LIKE query condition.
  2. Injecting a New Query: DROP TABLE products; is a new SQL statement, which, if executed, would delete the entire products table.
  3. Commenting Out the Rest: – comments out the remainder of the query, preventing any syntax errors from the leftover part of the original query (%’;).

The end result of this is that the attacker is able to eliminate the contents of the entire products table, destroying all data in the process without having proper access to the database. This is only one variation of exploiting this security vulnerability, more complex versions can leverage this process to escalate privileges or exfiltrate data from the table.

Dangers of SQL Injection

The most obvious risk of SQL injection attacks is having sensitive information leaked via the browser. Most applications have controls limiting the data that a user has access to. SQL injection attacks allow attackers to circumvent these controls and query the database like the application. This type of data breach can lead to legal and compliance penalties depending on the variety of sensitive data leaked. 

However, the risks of these attacks go far beyond data loss, as this elevated privilege can also be used to modify or delete data in the database server. Creative attackers can use this to modify information in the user table and change a user’s username and password. This will allow them to masquerade as a legitimate application user with more elevated privileges to conduct their attacks without setting off alerts. Using this attack style may also enable the internal database privileges to be targeted to create or modify existing database users and their permissions to log in directly to the database.

How to Prevent SQL Injection

Part of why SQL injection attacks have persisted so long as a threat to web application security is that prevention requires a multi-layer strategy. The first layer starts with input validation and sanitization, eliminating characters that could break out of SQL or allow other injection attacks. The injection risk is significantly reduced by ensuring all user input is thoroughly checked and cleansed of potentially harmful data. 

Building on this tactic is the use of parameterized queries and prepared statements. These secure coding practices effectively separate SQL logic from user inputs, nullifying the risks associated with dynamically generated queries. 

The final layer is adding regular security audits and testing to verify that the existing controls sufficiently stop these attacks. Leveraging automated tooling, organizations can conduct vulnerability assessments against their applications to identify areas where sanitization methods are insufficient to prevent such attacks. 

Proactively Stopping Injection 

Developing secure applications demands tools that can pinpoint vulnerabilities with precision. Probely stands out in this arena, capable of detecting over 3000 types of vulnerabilities, including critical ones such as XSS and SQL injections. It’s designed to proactively unearth and address potential security issues by seamlessly integrating with development workflows. This integration streamlines the process, offering automated and continuous security assessments that boost efficiency. By incorporating Probely, developers can fortify their applications at every stage of the development lifecycle, ensuring they are robust enough to securely manage your organization’s most confidential data.

Learn more about how Probely can help you secure your applications by trying out a risk-free demo.


What is the role of a Web Application Firewall (WAF) in preventing SQL Injection?

A WAF helps monitor and filter SQL injection attempts, acting as an additional security layer for web apps.

Can SQL Injection affect NoSQL databases?

While syntax differs, NoSQL databases can also be vulnerable to injection attacks, especially through poorly sanitized inputs.

Is SQL Injection only a risk for websites with login pages?

No, any part of a website interacting with a database, not just login pages, can potentially be vulnerable to SQL Injection.