A Beginner’s 4 Step Guide to SQL Injection Attack and Prevention


In the initial days of the internet, websites were simple; they had no JavaScript, zero CSS, and only a few images. As the digital world grew, the structure of web pages evolved as well. Today, new server-side scripting languages, CGI, and web designs are present on every website, making them highly intuitive and user-friendly. These websites also store user input and site content in databases, making every popular server-side scripting language to add SQL database support. 

But as databases became integral, SQL injection websites attacks too became evident. One of the most challenging issues in data integrity and confidentiality, SQL injection cyber-attack is a vulnerability that exploits the databases. If you’re on the journey to becoming a data scientist or a security expert, you need to know what these SQL injection attacks are and how you can prevent them. This article is a comprehensive beginner’s guide for understanding everything about the SQLI attack as a layman who is just starting to learn about them.

  1. What is SQL Injection?
  2. What are the types of SQL Injections?
  3. What are some SQL Injection examples?
  4. How can businesses perform SQLI Prevention?

1. What is SQL Injection?

SQL Injection, also SQLI, is a prevalent attack vector that uses malicious SQL code to manipulate the backend database in an attempt to access information that is not supposed to be displayed. The information may fall under any category, including but not limited to confidential business data, customer details, and user lists. Although this vector can harm and attack any SQL database, websites are the frequent targets of such an attack. Even a simple SQL injection attack code could have a huge impact on the enterprise.

Often, successful SQLI results in exposing the organization data, unauthorized viewing of user lists, deleting entire data tables, and gaining administrative rights to a database, which are also part of a SQL injection cyber-attack and are highly detrimental to businesses. Companies can rely on SQL injection attack tools to detect and prevent such breaches.

2. What are the types of SQL Injections?

There are several methods to exploit SQL vulnerabilities by attackers. Most of these hackers rely on errors, conditioning, and timing to plan their attack to retrieve and modify the information. The SQL injections attack types are based on the methods these attackers employ to access backend data and damage their potential.

A) In-band SQLI

Under this SQL injection attack type, attackers use a single communication channel to launch the attack and accumulate the results. In-band SQLI is such a simple SQL injection attack that hackers rely on for its efficiency and commonly use it.

In-band SQLI is further divided into two sub-categories:

1. Error-based SQLI:

Attackers exploit an error-based SQL Injection vulnerability by performing actions that make the database produce error messages. Hackers can then potentially use the error message data provided by the database to retrieve information, such as table names, content, and about the structure of the database. Usually, disabling error messages from displaying on the production system works to prevent attackers from gathering sensitive information.

2. Union-based SQLI:

This SQL Injection attack makes use of the UNION SQL operator that merges multiple select statements produced by the database to get a single HTTP response. This response may contain confidential data for attackers to steal.

B) Inferential (Blind) SQLI

Under this SQLI attack type, the hacker sends data payloads to the server and inspects the server response and behavior to learn about its structure. Blind SQLI attack gets its name from the fact that data does not transfer from the website database to the attacker, and they cannot see the information about the attack in-band.

Blind SQL injection attack is typically slower to run as it relies on the server response and its behavioral patterns.

Inferential SQLI is further divided into two sub-categories:

1. Boolean-based SQLI:

  • Often, the SQL query sent by attackers that returns an error does not allow them to extract any information from the vulnerable application. But when some sections of the HTTP response show changes, it helps the attacker determine whether the input parameter is susceptible and allows data extraction.

2. Time-based SQLI:

  • Hackers send SQL queries to the database, making the database wait (for a few seconds) before it can respond. The page will instantaneously reload if it is not vulnerable; if it is vulnerable, it will take longer than usual to load. Based on this response, the attackers can determine if the query was true or false without depending on the database’s information.

C) Out-of-Band SQLI

Under this SQLI attack type, attackers can send data directly from the database server to a machine controlled by them. Out-of-Band SQLI attacks can only be performed when certain features are enabled on the web application’s database server.

Out-of-Band is run by attackers when they cannot use the same channel to send and receive information, or when a server is slow to respond to their actions. This technique counts on the server’s capacity to create DNS or HTTP requests to transfer data to an attacker. The attackers don’t need to see the result of the injection; instead, they can wait for the database server to send a request to them.

3. What are some SQL Injection examples?

Typically, there are several ways attackers can execute an attack vector. Here we’ll provide you with a few SQL Injection attack examples to understand how SQL Injection attack works. Usually, the attacker who wishes to perform a SQL injection attack begins by manipulating a standard SQL query to exploit non-validated input vulnerabilities in a database.

For example, a database consists of several types of items in a shop’s inventory. If a data analyst wishes to pull out information about a particular product, he/she would need to put in the below-mentioned SQL Injection attack query.

SELECT ProductName, ProductDescription, ProductVendor

FROM ItemList

WHERE ProductCode = ‘Code of the Product’

The above SQL injection attack code helps the attacker to pull out the confidential details of an item. They just need to replace the ‘Code of the Product’ with the number 1099 and fetch it. Such code is often run as an SQL injection attack test to see if it gives any results.

If an attacker decides to breach this inventory database, they would most likely alter the SQL query to display all the products’ details. The sample SQL Injection attack would look like this:

SELECT ProductName, ProductDescription, ProductVendor

FROM ItemList

WHERE ProductCode = 1099 OR 1=1

Here, statement 1=1 is always true, making the query return all of the product information in the database, including those that hackers are unauthorized to access. This is known as a 1-1 SQL Injection attack.

In another SQL Injection attack example, attackers can leverage incorrectly filtered characters to alter SQL commands and even use a semicolon to separate the two fields. The sample SQL injection attack would look something like this:

SELECT ProductName, ProductDescription, ProductVendor

FROM ItemList

WHERE ProductCode = 1099; DROP TABLE USERS

The SQL injection attack query would result in the entire user database to get deleted.

There is yet another simple SQL Injection attack example that uses a UNION SELECT statement that combines two unrelated SELECT queries to fetch data from different database tables. The sample SQL injection attack would look something like this:

SELECT ProductName, ProductDescription, ProductVendor

FROM ItemList

WHERE ProductCode = ‘1099’ UNION SELECT Username, Password, Security code from Users;

This SQLI attack query would result in pulling out the product details of the product numbered 1099 and combining it with another query that pulls the name, password, and security code of all the users.

In addition to the samples mentioned above, there are many other ways for attackers to alter SQL queries and exploit database vulnerability to fetch information not authorized for them to access.

4. How can businesses perform SQLI Prevention?

Until now, we discussed every SQLI attack and examples to carry SQLI attacks. But there are also solutions for SQL Injection attacks. In this section, we’ll discuss the SQL Injection attack prevention. One of the best methods to detect and prevent attacks is to restrict database access as much as possible and keep different databases for different purposes and information storage. 

As the first step to mitigating such attacks on databases, coders must input validation (sanitization) to identify illegitimate user inputs. However, while validation is a useful practice, it still doesn’t map out all valid and invalid inputs. Hence, a web application firewall (WAF) is usually employed to filter out SQL injection attacks and other online threats.

WAF depends on a large and updated list of meticulously formulated signatures, allowing it to pinpoint and remove malicious SQL queries surgically. Such lists usually hold signatures to address specific attack vectors and constantly introduce blocking rules for every newly discovered vulnerability. Also, as modern web application firewalls are integrated with other security solutions, WAF can receive information from such firewalls and boost its already secure environment for SQL injection attack prevention.

Additionally, there are several SQL injection attack tools that help enterprises in SQLI attack prevention. You can also use the SQL injection attack practice site to look for open holes or vulnerabilities in your database.


Enterprise security is an essential part of any business model; protecting databases, confidential client information, and research datasets are crucial to any organization’s success. SQLI attack works to identify the loopholes that might be present within or outside of the enterprise.
All this information about cyberattacks assists security experts in creating exceptional strategies to prevent issues. If you’re interested in SQL Injections and other Cyber Security threats and their defense, then Jigsaw Academy’s online 520-hour-long Master Certification in Cyber Security (Blue Team), India’s first program on Defensive Cyber Security, can offer you a professional understanding and hands-on experience of Cyber Security concepts.

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