SQL Injection Is an Attack Used by Hackers to Inject Malicious Codes in SQL Statements
Data is among the most critical components in today’s information systems. For example, SQL (Structured Query Language) is used for all types of interactions, such as retrieving and updating a user’s critical information.
As technology grows, so does cyberattacks. SQLi (SQL Injection) is a type of attack that hackers use to inject harmful code into an existing SQL statement.
If you’re wondering what SQL Injection means, then keep reading.
What Is a SQL Injection Attack?
SQL Injection is one of the web security vulnerabilities that attackers use to interfere with the queries used by an application to deal with critical data stored within the database, such as customer’s data or data of your website like products and their details. Likewise, SQL Injection allows hackers to view data that isn’t possible to recover once the attack is successful.
It’s a type of injection attack targeted towards a web application in which the attacker provides a malicious SQL (Structured Query Language) code to a user input box of any web form with the motive of gaining unauthorized and unlimited access. Likewise, the attacker’s input is transmitted via SQL query so that it comes across as a legit SQL code.
In other words, SQL Injection is a type of attack where hackers poison dynamic SQL statements that successfully run the query triggered by them. For example, an attacker may gain access to your site database and delete any table.
Usually, SQL Injection is the result of designing flaws due to poorly designed web applications. So, attackers take advantage of it by exploiting SQL statements and implementing malicious SQL codes. Sometimes, attackers can even escalate a SQL injection attack that can compromise the server or back-end infrastructure – or perform other attacks like denial-of-service attacks.
How Does SQL Injection Work?
SQL Injection attacks are usually performed through web pages or any input in the application. For instance, input forms are often seen in features like form fields, search boxes, and URL parameters. And SQL Injection attacks target vulnerabilities that are present within dynamic SQL statements. Therefore, bad attackers first identify vulnerabilities within an application or web page. And after that, they locate a target, create malicious payloads and send their content for executing malicious commands.
In many cases, attackers even use an automated program that carries out a SQL injection attack on behalf of them, where all they need to do is to provide the URL of the targeted website. Then data gets stolen from the victim.
Different Types of SQL Injection Attacks
According to the OWASP Top 10 list, SQL injection is the number one threat for web applications, and SQL injection can also get exploited in different ways.
Some common methods for executing a SQL injection are executing commands on the database server, retrieving the database based on error messages, or interfering with the query logic.
Union Based SQL Injection
This is a popular SQL Injection method among attackers. During a union-based SQL Injection, hackers extract data through the database by extending the original query results. For instance, it uses the UNION SQL operator that integrates two different SELECT statements into a single result and returns it as the response.
Blind SQL Injection
Blind SQL Injection is usually more sophisticated and harder to perform than other types of SQL Injection attacks. In this attack, hackers perform an attack when the targeted victim receives generic error messages.
Furthermore, the blind SQL injection differs from other SQL injections, because they retrieve information from the database. For example, in a blind SQL injection, hackers query the database for true or false questions, and later the answer is determined based upon the received response. Lastly, time is taken to retrieve a server response when it’s a time-based attack.
Boolean Based SQL Injection
This is another type of SQL injection method where an attacker overwrites and changes the existing query’s logic and conditions with their malicious ones. It’s usually used for authentication or permission queries, where the database gets tricked into believing that they have granted correct credentials or permissions.
Likewise, this Boolean-based SQL injection is used with the blind SQL injection. It processes the elimination for extracting data from the database—for example, sending numerous requests, where every request consists of a condition slightly different from its practices. So, the attacker can determine whether the database is stored based upon the results or not.
Error Based SQL Injection
As the name implies, with the error based SQL injection, attackers exploit database errors through a web page or an application that has been triggered through an un-sanitized input.
In this Error-based SQL injection attack, hackers use error messages that return full query results and critical information through the database. Furthermore, this method is also used to find out if a web application or website is vulnerable and find out other information that helps in restructuring malicious and harmful queries.
Time-Based SQL Injection
In other SQL Injection methods, hackers simply get the text as it’s returned. On the other hand, when attackers can’t retrieve information through the database server, they opt for time-based SQL injections for getting results. It usually works by using operations that take a longer duration to complete – usually in seconds.
Likewise, these time-based SQL injections are commonly used by attackers when trying to determine whether vulnerabilities are present within targeted web applications or websites, along with Boolean-based methods at the time of Blind SQL injections.
Example of SQL Injection Hack
There’s a wide variety of SQL Injection vulnerabilities, techniques, and attacks. And which arises in which situation is not easy to predict.
In this SQL injection example, we try to log in by comparing usernames and passwords with those stored within the database.
This example perfectly sums up what should be avoided. This SQL query consists of more than one flaw by design. And, due to this, it’s vulnerable to SQL injection attacks. And, to make it worse, it’s not using salted or hashed passwords.
In the example mentioned above, the SQL query is built using concatenating the username and password directly within the query.
Likewise, it becomes easier for attackers to escape the quotes and inject other SQL operations. For example, display true if the certain username is admin. And, because of this, an attacker can successfully gain access to an admin account.
Here’s How to Spot an SQL Injection Attack
SQL Injection attacks aren’t easy to spot. Like other cyberattacks, remote code injection, cross-site scripting and SQL Injection doesn’t leave behind any server traces. On the contrary, in SQL injection, genuine queries are exploited. Many times, it’s detected once the attacker has completed their malicious activity or gained admin access.
Nonetheless, by taking necessary security measures and regularly monitoring your site database and its queries, you can spot if any attacker is running a malicious SQL injection on your site or not.
Steps to Prevent SQL Injection Attack
Nowadays, cyberattacks happen daily, and attackers also keep on getting more advanced as the technology advances. For instance, undisclosed, zero-day vulnerability or unpatched components can become a reason for a wide array of SQL injections at the time of targeted attacks.
Put simply, keeping all your third-party software and components updated is one of the easiest ways to prevent SQL injection attacks. However, some techniques can help you prevent SQL injection attacks, and they’re as follows:
Make Use of Prepared Statements with Parameterized Queries
Prepared statements ensure none of the dynamic variables you require within a query escapes their position, and that’s one of the main reasons for using it. Also, the main query is defined early along with the arguments and their types afterward.
Since the query is aware of what type of data should be expected, like a string or number, they know exactly how to integrate it into the query without creating any further issues.
In the above example, even if the username or password variables try to escape their query, the prepared statements will properly escape their characters, which will prevent any unexpected behavior or an attack (such as a SQL injection).
Stored procedures are frequently used operations stored in the database while varying only with the arguments. Furthermore, stored procedures make it harder for attackers to execute any malicious SQL queries, as it’s not possible to insert anything within the queries dynamically.
Allowlist Input Validation
Make a rule for not trusting user-submitted data. Perform allowlist validation for testing user input against existing, known, approved, and defined input. And, whenever you receive any data that fails to meet assigned values, reject it as it’ll prove helpful in protecting your web application or website from malicious SQL injection attempts.
In other words, all types of user inputs within an SQL query have a risk of an SQL Injection. So, it’s recommendable to avoid trusting user inputs and instead treat all input types, including authenticated or internal user input, like you’re treating public inputs.
Least Privilege Principle
As the name implies, provide the access controls according to the role. Avoid granting access to any admin type access to application accounts. It’ll help your website to prevent security threats. And, to implement such a principle and prevent your site from SQL injections, some steps you can take include:
- Provide access for the specific time period. For instance, until the given action is not completed.
- Prevent giving any type of access right that needs to be given to the administrator.
- Minimize access to all database account that are present within your environment.
- Provide privileges based on the tasks to be performed.
Security Training & Maintaining Awareness
Provide appropriate security training to all your developers, DevOps, SysAdmins, and QA staff. It’ll help keep your web application safe, as everyone will get proper training and instructions on the risks regarding SQL Injections.
Upgrade with the Latest Technologies
Avoid using older web development technologies, as they don’t come with SQLi protection. Instead, it’s recommended to use the latest development environment, language, and the latest technologies associated with it. For instance, in PHP, make use of PDO rather than MySQLi.
Avoid Blacklists & Use Whitelists
Prevent filtering user input based upon blacklists because experienced attackers mostly find a way to bypass blacklists. Instead, try verifying and filtering user input through rigorous whitelists.
Make Use of a Waf (Web Application Firewall)
Deployment of a Web Application Firewall is among the proven methods that help secure your site from online attacks. For instance, a WAF based upon rigorous rules can effectively detect and prevent attacks such as SQL injection and other new vulnerabilities.
Prevent Displaying Database Errors
It’s recommended to avoid displaying database errors to users because an attacker can use such error messages to gain database information that can lead to a successful SQL injection attack.
Update Your Database with the Latest Patches
Update your database with all the latest patches as it helps to prevent attackers from exploiting bugs or any weakness present within older versions.
Prevent Storing Data in Plaintext
Prevent storing data in plaintext and instead encrypt critical data that are stored within the database and salt all the encrypted hashes, as it works as an advanced protection method if an attacker successfully gains access to your important data.
SQL Injections may get introduced by your developer or through any external modules, libraries, or software. It’s recommended to regularly scan your web applications using a vulnerability scanner such as the multipurpose tool CodeGuard backup.
SQL injection is one of the OWASP Top 10 vulnerabilities. It’s a popular cyberattack that’s known for targeting your website’s sensitive data.
However, you can overcome this SQL injection attack by ensuring that your website data is properly encrypted. Likewise, you should regularly protect and test your website by taking proper steps such as keeping your site updated with all the available patches, providing adequate training and maintenance awareness to employees, and performing regular scanning.