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How Does an SQL Injection Attack Work? (In-Depth Analysis, Scenario, & Mitigation Process)

SQL-Injection Attack

What is an SQL (Structured Query Language) Injection Attack?

Since its introduction, the SQL Injection bug has been recognized in the OWASP Top 10 list of the most frequent and widely utilized bugs as one of the most dangerous concerns for data confidentiality in web applications. It is a method of injecting malicious content into original SQL statements. These injections allow malevolent individuals to overcome existing security protections and get unauthorized access to data, such as client data, copyrighted material, or personal details. Understanding SQL Injection Attacks is an important step in your learning process of Web Application Penetration Testing. 

SQL Injection attacks could have a disastrous impact on any system that allows a SQL database and handles data, including webpages, workstations, and mobile apps.

How does SQL Injection Work?

SQL Injections are often carried out either website or app input. Input forms are frequently encountered in features such as search bar, input fields, and URL properties.

An SQL Injection vulnerability affects a web page or web application that uses user input directly in a SQL query. An attacker must first find vulnerable user inputs within the web page or application before launching a SQL Injection attack. The attacker can create input content. This type of content is known as a malicious payload, and it is an essential part of the attack. Malicious SQL commands are executed in the database after the attacker sends this content. These types of attacks are often put to work in web application penetration testing processes.

In certain circumstances, bad actors may simply use an automated tool to do an SQLi on their behalf—all they need to do is provide the URL of the specific website to retrieve hacked information from the target. As a result, a successful SQL Injection attack can have serious ramifications.

  • Attackers can use SQL Injections to discover the credentials of other users in the database. They can then use these users’ identities to impersonate them.
  • SQL allows you to choose and output data from a database. An SQL Injection flaw could give an attacker complete access to all data on a database server.
  • SQL also allows you to change and add data to a database. An attacker could use SQL Injection in a financial application to change balances, void transactions, or transfer money to their account.

Types of SQL Injections

SQL Injections are categorized into three types:

  • In-band SQLi (Classic)
  • Inferential SQLi(Blind)
  • Out-of-band SQLi

In-band SQLi: The attacker used the same communications channel to launch cyberattacks and collect data. In-band SQLi is one of the most common types of SQLi attacks due to its simplicity and speed. This approach is divided into two sub-categories:

  1. Error-based SQLi: The attacker carries out things that cause the system to generate error codes. The attacker can leverage the data given by these error codes to learn about the database.
  2. Union-based SQLi: This method uses the UNION SQL operator, which combines numerous select queries issued by the database to produce a single HTTP response. This response may hold information that the attacker can use.

Inferential SQLi(Blind): To understand the server’s design and structure, the attacker delivers data payloads and examines its reaction and behavior. Because the data is not sent by web page to the attacker, the attacker cannot access data about the attack in-band. The following are the several types of blind SQL Injections:

  1. Boolean: The attacker creates a SQL query to the database, requesting that the application give results. The outcome will differ based on whether the query is correct (True) or wrong (False). The information in the HTTP response will vary or remain unchanged depending on the outcome. The attacker can then verify if the message delivered a right (True) or wrong (False) result.
  2. Time-based: The attacker creates a SQL command to the database, which causes the database to pause (in seconds) before responding. Then the attacker can identify whether a command is true or false based on the time it takes the system to react. Depending on the results, an HTTP response will be issued either immediately or after a hold time.

Out-of-band SQLi: The attacker can only carry out this type of attack if certain functionalities on the database server used by the web application are enabled. This type of attack is typically employed as a backup to in-band and inferential SQLi attacks.

Out-of-band SQLi is used when an attacker can’t launch an attack and gather information over the same channel, or when a server is too slow or unstable to perform these actions. These methods rely on the server’s ability to send DNS or HTTP requests to send data to an attacker.

SQL Injection Attack Scenario

As we discussed above, SQL injection is a method that allows an attacker to insert SQL commands into a SQL query via an HTML form. Injected SQL instructions can modify SQL statements and harm a web application’s integrity. For a better understanding, let’s look at a simple example.

Example: Imagine we have a SQL query that will choose the specific user based on his login information. If there is no way to prohibit harmful user input, the user can provide it to attack the application.

A basic harmful query might look something like this:

->SELECT * FROM users WHERE username = “admin” ‘OR 1=1 and password = “abc”

This SQL statement is accurate. Because where 1=1 is always authentic, it will retrieve all rows from the table “users.” As a result, an attacker can quickly obtain all of the login information from the database.

How to Prevent an SQL Injection Attack

SQL Injection attacks are brutal to avoid. Specific preventive strategies vary depending on the SQLi threat type, the SQL database system, and the web application. However, there are some specific strategic concepts that you should adhere to in order to keep your online application secure.

Step 1: Training and Awareness

To ensure the security of your web application, everyone involved in its development must be aware of the potential risks connected with SQL Injections. All of your developers, employees, DevOps, and System Administrators should get the necessary security training.

Step 2: Don’t Put Your Faith in any User Input

Consider all user input to be untrustworthy. Any input data used in a SQL query increases the danger of SQL Injection. Treat input from authorized or insiders in the same manner as you would treat public feedback.

Step 3: Use Whitelists Rather than Blacklists

Do not use blacklists to restrict user input. A skilled attacker will always find a way through your blacklist. If necessary, only implement rigorous whitelists to check and filter user input.

Step 4: Adopt the Latest Technologies

SQLi protection is not available in older web technologies. Use the most recent version of the development platform and language and the most recent technologies connected with those environments and languages.

Step 5: Use Strategies that have been Proven Effective

Don’t try to create SQLi security from the initial concept. Most modern development platforms have features in place to protect you from SQLi. Rather than trying to invent the wheel, make use of existing mechanics.

Step 6: Scan Regularly

SQL Injections can be supplied by your developers or by a third-party toolkit. You should use a web vulnerability scanner to scan your web apps regularly.

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My name is Pooja Rawat. I have done my B.tech in Instrumentation engineering. My hobbies are reading novels and gardening. I like to learn new things and challenges. Currently I am working as a Cyber security Research analyst in Infosectrain.