What is SQL Injection Attack, Its Types & How to Prevent It?

Written By Sambita Panigrahy  
Anuraag Singh
Approved By Anuraag Singh 
Published On October 3rd, 2023
Reading Time 11 Minutes Reading

Definition: SQL injection attack or SQLi in short is one of the most serious web application security risks as per Open Web Application Project. A malicious SQL code is injected into an application in this kind of hack, enabling attackers to see or alter databases. It enables the hacker to obstruct a database query that an application makes. As a result, they can compromise the underlying server or other backend infrastructures, or at worst perform a denial of service attack.

Every website or web application that makes use of a SQL database, such as MySQL, Oracle, SQL Server, or another one, may be vulnerable to a SQL Injection flaw. Your sensitive data, including customer information, personal information, trade secrets, intellectual property, and more, could be accessed by criminals without your permission. One of the oldest, most common, and most harmful online application vulnerabilities are SQL Injection attacks. Injections are ranked as the top danger to web application security by the OWASP organization (Open Web Application Security Project) in their list of the top 10 threats for 2017.

This is a cyberattack that takes the help of SQL queries to execute the attack.

So, What Are SQL Queries?

Accessing databases and modifying them to give user-customizable data representations requires the standardized language SQL. Data retrieval, updates, and record removal are just a few tasks that may be carried out using SQL queries. Many SQL components, such as queries that retrieve data using the SELECT statement and user-supplied parameters, perform these functions.

The SQL database query for a typical eStore might resemble the following.

SELECT ItemName, ItemDescription
WHERE ItemNumber = ItemNumber

Impact of SQL Injection Attack

SQL injection can have a variety of negative repercussions on a company. A successful attack could result in the unauthorized access of user lists or the total erasure of tables. A corporation would suffer greatly if an attacker were to get administrative access to a database, for example.

When calculating the potential cost of an SQLi should sensitive data like phone numbers, addresses, and credit card details be compromised, it’s critical to take the loss of client trust into account.

This cyberattack has a significant negative impact on an organization. Mostly they target sensitive and confidential information.

Here are some of the negative consequences an organization may face after a successful SQL injection attack.

  • Exposes Important Business Data: By using SQLi to retrieve and modify data, attackers run the risk of disclosing critical company information that is kept on the SQL server.
  • Consumers’ privacy could be compromised depending on the information kept on the SQL server. An attack could reveal sensitive user information, such as credit card numbers.
  • If a database user has these rights, an attacker can use malicious code to enter your system, giving an enemy administrative access. Create a database user with the fewest rights feasible to protect yourself against this type of vulnerability.
  • Giving an Attacker Full Access to Your System: If you check user names and passwords with flimsy SQL statements, an attacker could access your system without being aware of a user’s credentials. An attacker can do more harm if they have full access to your system and can access and alter sensitive data.
  • Your data’s integrity could be compromised since an attacker could alter or remove data from your system using SQL injection.

Before moving ahead with the prevention techniques, it’s important to learn about different types of SQLi attacks so that you will know what you are up against.

Types of SQL Injection Attacks

Businesses may better prepare for attacks and fix vulnerabilities by understanding cybersecurity risks. Let’s examine the many SQL injection attacks, which may be divided into three types: in-band, inferential, and out-of-band SQL injection.

sql injection attack

1. In-band SQL Injection 

SQL injection in-band attacks are the most prevalent kind. With this type of SQL injection attack, the attacker and data collector use the same communication channel. The most prevalent types of in-band SQL injection attacks use the following methods:

  • Using an SQL command to request an error message from the database server, attackers can utilize this technique to obtain details about the database’s structure. While error warnings are helpful when creating a web page or application, they eventually provide a security risk since they reveal database information. You can turn off error messages after a website or service is operational to avoid this issue.
  • Union-based SQL injection: With this method, attackers combine several select statements into a single HTTP response by using the UNION SQL operator. This method can be used by an intruder to retrieve data from the database. The most prevalent type of SQL injection method needs more security precautions to prevent than error-based SQL injection.

2. Inferential SQL Injection

Because the website database does not send information to the attacker, unlike in-band SQL injection, inferential SQLi is also known as blind SQLi. Alternatively, by delivering data payloads and watching for the response, a malicious user can discover the server’s architecture. Because they can take longer to complete, inferential SQL injection attacks are less frequent in comparison with the previous type. The following methods are used by the two types of inferential SQL injection attacks:


  • With the boolean injection approach, attackers send a SQL query to the database and watch the response. Depending on whether the data in the HTTP response was altered, attackers can determine if a result is true or false.
  • Another technique Attackers use is the time-based injection to force the database to delay a predetermined number of seconds before replying to a SQL query. The number of seconds that pass before a response might be used by attackers to assess if the outcome is genuine or false. For instance, if the initial letter of the name of the first database is A, a hacker could execute a SQL query that orders a delay. The attacker will then be aware that the query is accurate if the response is delayed.

3. Out-of-Band SQL Injection

This particular type is the least prevalent attack in SQL injection. Malicious individuals conduct this type of SQL injection attack using a different communication channel than they do for data collection. If a server is too sluggish or unreliable for inferential SQL injection or in-band SQL injection, attackers will utilize this technique.

How does a SQL injection or SQLi Attack Work?

Before launching an SQLi attack, an attacker must initially locate weak user inputs on the website or in the web application. Such user input is immediately used in a SQL query on a web page or web application that is vulnerable to this attack. Input content can be produced by the attacker. 

The combination SQLi and command execution attack functioned as follows, according to a report commissioned by Accellion:

  • To access document root.html, the attackers used SQL Injection. The Accellion FTA database’s encryption keys were then downloaded.
  • Attackers created legitimate tokens using the keys, and then they utilized those tokens to access further files.
  • Attackers were able to run their commands by taking advantage of a vulnerability in the sftp account edit.php file that allowed operating system command execution.
  • /home/seos/courier/oauth.api on the server is where attackers constructed a web shell.
  • They used this web shell to upload a fully customized web shell with highly customized tooling for data exfiltration from the Accellion system to the disc. This shell’s scientific name is DEWMODE.
  • Attackers on the Accellion FTA system used DEWMODE to extract a list of available files from a MySQL database. They then published the files and their metadata on an HTML page.
  • Attackers used URL parameters that were encoded and encrypted to execute file download requests that included requests to the DEWMODE component.
  • These requests can be approved by DEWMODE, who will then remove the download requests from the FTA weblogs.

Symptoms of SQL Injection Attack

It’s hard to find any signs of a successful SQLi attack. However, it sometimes shows outward signs that we may count on. They are;

  • Your inbox may fill with a huge number of email requests from your webpage contact form.
  • Unknown popups and errors.
  • Ads redirecting to suspicious websites.

Real-World Example of SQL Injection Attack

Many enterprises have suffered from SQLi over the years. Other well-known instances include:

Example 1 – The year 2019 (Fortnite)

There are more than 350 million players in the online game Fortnite. A SQL injection bug that allowed attackers access to user accounts was found in 2019. The issue has been resolved.

Example 2 – The year 2018 (Cisco)

2018 saw the discovery of a SQL injection flaw in Cisco Prime License Management. Attackers were able to acquire shell access to computers where the license management was installed because of the vulnerability. Since then, Cisco has patched the issue.

Example 3 – The year 2014 (Tesla)

Security researchers said in 2014 that they had used SQL injection to compromise Tesla’s website, obtaining administrative rights and stealing user information in the process.

How to Detect SQL Injection Vulnerabilities?

By manually running some systematic tests, you can detect SQLi attack entry points in the application.  You can do that by submitting the below points.

  • Single Quote character (‘) and search for any errors.
  • Some SQL-specific syntax to evaluate the base value of the entry point. Look for any systematic differences in the application response.
  • Boolean conditions, For example, OR 1=1 and OR 1=2 to find any differences in the application response.
  • Payloads for triggering time delays within a SQL query. Observe the difference in the response.
  • Configure your web application to log all SQL errors and exceptions. Monitor these logs for any unusual or unexpected SQL queries.

Techniques to Prevent SQL Injection Attacks

Key guidelines to help safeguard websites and web applications include the following:

Staff education:

The team in charge of your online application should become more aware of the hazards associated with SQLi, and all users should receive the requisite role-based training.

Constrain user input:

An SQL query that uses user input carries some risk. As long as it hasn’t been confirmed, treat input from authenticated and/or internal users the same as public input. Provide SQL database connection accounts simply the bare minimum of rights. Employ allowlists, not blocklists, as a routine procedure to validate and filter user input.

Use the newest versions:

To maximize protection, it’s crucial to use the most recent version of the development environment because earlier versions might not have the most up-to-date security measures. Install the newest software and security updates as soon as they become available.

Constantly scanning web applications:

Implement thorough application performance management tools. Web applications can be regularly scanned to find and fix possible flaws before they cause major harm.

Use a firewall:

To block SQLi and other online attacks, a web application firewall (WAF) is frequently utilized. An extensive and regularly updated list of signatures is used by a WAF to screen out fraudulent SQL queries. Further, the list typically contains signatures to counteract particular attack vectors, and it is frequently patched in response to vulnerabilities that are found.


Attacks using SQL Injection can take advantage of a company’s database and take over a database server that is hiding behind a web application. Now you are familiar with the definition, types of SQLi, and preventive techniques to avoid such attacks.

If you are looking for more advanced learning of ongoing cyberattacks, you can contact our cyber expert team.


Q- How dangerous SQL injection attacks can be?

The consequences of an SQL injection can be severe, as a successful attempt of such an attack may lead to a complete compromise of a system. So, this attack is pretty much dangerous.

Q- How common these SQLi attacks are?

The complexity of web applications, widespread use of SQL, lack of secure coding practice, etc. are some of the factors that made SQLi attacks prominent for years. So, you can say that these attacks are common in today’s digital world.

Q- What can attackers do with SQL injection?

Attackers can perform various malicious actions, including unauthorized data retrieval, data modification or deletion, privilege escalation, and even taking control of the database or the entire application server.

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