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What is a SQL Injection? How to prevent it?

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SQL Injection is one of the common cyber security attacks used to attack data-driven applications. It uses SQL to inject code into the application, manipulate the data in the database, or access confidential information, which can have severe consequences on the business.

These attacks are mostly made on web applications, especially one that uses PHP or ASP. Continue reading the article to explore more about SQL Injections.

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What is SQL Injection?

SQL Injections are also known as SQLI. Usually, when you ask the user for some input such as their user-id, a SQL query is created which runs on the database. This query can be tampered with by the attacker through which the attacker can get access to the database.

Before going into more details, let’s understand the SQL queries first. It will help us understand what the attacker can do or gain access to via the injection attack.

What is a SQL Query?

SQL stands for Structured Query Language. Using the SQL, you can insert some data into the database, fetch the data, and delete some data or records from the database of your application. There are various SQL queries to perform these actions, such as “insert into” or “select” statements. Let’s see an example to understand the SQL query better.


This query will fetch all the customer data whose id is 1501 from the customer table.

What is a SQL Injection? How to prevent it?

For example, let’s assume the attacker changes the value of CUST_ID to, say, 1601. Due to this, the data that was supposed to be fetched for a customer with id 1501 will be replaced by another customer’s data with id 1601.

The attacker can add some smart inputs to the query, such as “OR 1=1”.


Here, 1 is always equal to 1, and hence yield’s true. The ‘OR’ operator used ensures that the overall result is true if any result is true. Thus, this query then returns all the records in the customer table.

What is a SQL Injection? How to prevent it?

Now, what if the customer table has some passwords in it? The attack will make all the sensitive data of a customer stored in the table accessible to the attacker.

Also read: What is the difference between SQL and MySQL?

Impact of SQL injection attacks

The impacts that a SQL Injection attack can have on an application or a database can be very severe.

  • The attacker can disclose all the data in the system, including confidential data.
  • The attacker can tamper with the existing data.
  • If the attacker gets access to the user-id and passwords, he can spoof your identity and login into your account.
  • The attacker can delete all the data present in the system. Thus, making the system unaccessible to everyone.

The SQL Injection Attack can affect the triad of information security (Confidentiality, Integrity, and Availability) severely. Hence, it becomes necessary to build the applications so that the developers take care of preventing SQL Injection Attacks.

Also read: What is a Watering hole attack, and how is it carried out?

How to prevent SQL injection attacks?

You can prevent SQLI attacks by performing some practices on your application.

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  • Only ask for user input when required; avoid asking for unnecessary user inputs.
  • Validate the input from the user end and apply some constraints on them. It is challenging to add constraints and check on every input and affect the user experience, but you can put constraints on the common inputs. For example, a mobile number cannot have more than 10 digits.
  • Continuous keep testing your web application for some code vulnerabilities. If any vulnerability is found, take steps to fix them on priority.
  • Avoid using dynamic queries and use parameterized queries.
  • Use escaping scheme on the user input before putting the input into the query. So, for example: check if the user input has some special character like ‘=’ or ‘*’. And, if it does, then escape the character by using a ‘\’ sign. (The escaping may vary depending on the programming language used). The escaping will treat the symbol as a character, not as some operation.
  • Keep your development environment and packages up-to-date.

You can defend your application from SQLI attacks by following these basic procedures. However, you’ll have to take additional measures to ramp up your security and keep up with cybersecurity trends. Performing these or similar other steps will undoubtedly reduce your application’s risk or vulnerability. Thereby reducing the chances of attack.

Also read: What is a Credential-based cyberattack?

Chetali Shah

Chetali Shah

An avid reader and an engineering student. Love to code and read books. Always curious to learn new things :)