Cyber Security

Cybercriminals have various ways to attack their target systems, and SQL injection is a particularly insidious technique. So, what is SQL Injection? How does it work? How harmful is it? And how can you overcome it once you’re attacked by it?

If you have these questions, keep reading this article! We’ll explore them in detail, providing you with a comprehensive understanding of SQL injection, its impact, and the best practices to mitigate its associated risks.

Let’s go!

What is SQL injection (SQLi)?

An SQL injection attack (SQLi) is an injection attack in which malicious SQL code manipulates the queries an application sends to its database. This allows attackers to access confidential information, such as sensitive company data, user lists, and private customer details, that would normally be inaccessible to anyone.

In addition to gaining unauthorized access, an attacker can also edit, add, delete, or modify the SQL database inside, which is very dangerous as it can lead to data loss, data corruption, and unauthorized transactions. For example, an attacker could alter a database to change the price of a product to zero, allowing them to purchase items for free or manipulate financial records to cover their tracks.

How to Detect SQL Injection Vulnerabilities?

SQL injection vulnerabilities can be detected automatically and manually through testing methods that involve systematically probing every entry point in an application. Here are the manual methods to detect them:

1. Single Quote Character (‘): Inserting a single quote character and checking for errors or unusual responses. If the application shows an error, it could mean a vulnerability.
2. SQL-specific Syntax: Comparing the original value with a different value to find differences in the application’s responses. This could highlight a possible vulnerability.
3. Boolean Conditions: Using conditions like OR 1=1 (always true) and OR 1=2 (always false) to see if the application behaves differently. Changes in behavior could indicate a vulnerability.
4. Time Delay Payloads: Adding payloads that cause delays to see if the application responds slower. A slower response might indicate a vulnerability.
5. OAST Payloads: Using payloads that interact with external systems to detect vulnerabilities. Monitoring these interactions can reveal ways an attacker might unintentionally access the database.

On the other hand, automated scanners can quickly and reliably detect most SQL injection vulnerabilities by automatically testing various inputs and analyzing the responses for signs of vulnerability.

Types of SQL Injections

SQL injections have various types that attackers can use to exploit vulnerabilities in a web application’s database. Here are the most common types of SQLi:

Inferential (Blind) SQLi

Blind SQL injection works without allowing the attackers to receive the data directly. Attackers send specific data to the targeted service to observe its response. Understanding the server’s behavior and structure helps the attacker decide how to proceed, whether they intend to launch a DDoS attack or pose other threats.

There are two kinds of blind SQLi: Boolean-based, where the result depends on whether the SQL query is false or true, and Time-based, where the duration of the database’s response determines it.

In-band SQLi

In-band SQLi is when attackers use the same communication channel to both launch their attacks and receive the results. It’s popular because it’s simple and effective. There are two main types of SQLi:

1. Error-based SQLi: This type of attack triggers the database to produce error messages, which can reveal information about the database’s structure.
2. Union-based SQLi: Attackers utilize the UNION SQL operator to combine multiple select statements from the database into a single HTTP response.

Out-of-band SQLi

Out-of-band SQLi is an attack that can only happen if certain features are turned on in the database server used by the web app. It’s used as an alternative to other SQLi techniques.

Out-of-band SQLi happens when the attacker can’t use the same path to launch the attack and get information. This might occur if the server is too slow or unstable. In this case, the attacker relies on the server’s ability to send DNS or HTTP requests to share data.

How to Prevent an SQL Injection

SQL injection (SQLi) is one of the most common ways for attackers to exploit vulnerabilities in web applications. This is proven by the fact that approximately 42% of hacking attempts on public-facing systems involve SQL injections. This highlights the importance of being aware of it and taking measures to prevent SQL injection attacks.

Here are the general tips and steps to prevent SQL injections:

 Train and maintain awareness

To ensure web server security, everyone involved in its development needs to understand the dangers of SQL Injections. It’s essential to provide comprehensive security training to all developers, QA staff, DevOps, and SysAdmins.

Don’t trust any user input

SQLi can come from various sources, so all user input is potentially unsafe. Any user input used in an SQL query poses a risk of SQL Injection. Treat input from authenticated or internal users with the same caution as input from the public.

Use whitelists, not blacklists

Attackers will always be “creative” in finding ways to gain unauthorized access. That’s why it’s better to use a whitelist filter instead of a blacklist. If possible, validate and filter user input strictly using whitelists.

Adopt the latest technologies

As technology advances, older web development technologies are more likely to lack protection against SQLi. It’s advisable to use the latest version of the development environment, programming language, and associated technologies. For example, in PHP, choose PDO over MySQLi.

Employ verified mechanisms

There are already technologies for SQLi protection, so creating protection from scratch is unnecessary. Modern development technologies often offer built-in mechanisms to guard against SQLi. It’s better to utilize these existing mechanisms rather than trying to create your own.

Scan regularly

If you have a scanner to detect vulnerabilities in your system, including SQLi, use it regularly. Attacks can occur at any time and in various ways, so you must be cautious and scan your system regularly.

Frequently Asked Questions

Conclusion

SQLi has existed for decades, and while the number of incidents has decreased each year, there’s no harm in learning about it and how to prevent it. Understanding SQLi can help developers build more secure applications, protect against potential cyber security threats, and ensure the integrity and confidentiality of data.

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