7 Types of SQL Injection Attacks & How to Prevent Them?

SQL injection attacks are one of the most common but dangerous security threats that affect web applications directly. Cybercriminals manipulate the SQL database by injecting malicious code to get unauthorized access, breach data, and compromise the system. Knowing the different types of SQL injection is important to be able to differentiate them and to know how to detect and prevent each type.

This will help you strengthen your application and database security while safeguarding your company’s finances and reputation from SQLi threats. This article covers the list of SQL injections, their types, how to prevent them, and some real-world examples.

What Are SQL Injection (SQLi) Attacks?

SQL injection (SQLi) attacks happen when an attacker inserts malicious SQL-based code into an application’s input fields to be able to manipulate the database. This way, they can access your database without authorization, extract confidential data, change, add, or delete records, and compromise the whole system.

SQLi occurs mainly due to un sanitized user inputs, which allows malicious code to be inserted and executed. Once this happens, they can control your database, application, and the data stored inside it to launch further attacks or complete their malicious intent.

Why Is SQL Injection a Major Security Threat?

SQLi allows attackers to bypass basic authentication mechanisms to access your database directly and extract data. Once inside, they steal, modify, and delete your business-sensitive data, such as login credentials, customer records, and financial transactions.

It’s hard to trace SQLi attacks as they alter code logic, which makes detection and prevention difficult. They can also install malware to take the full system controls and cause website defacement, complete system failure, and ransomware infections. They can steal data, encrypt data, demand ransom, or expose your sensitive business data to the public to cause reputational damage. This may lead to data privacy risks, such as higher scrutiny from authorities, legal proceedings, and heavy fines.

How Do SQL Injection Attacks Work?

In SQLi, attackers exploit security vulnerabilities in an app’s SQL query execution, which could arise if you don’t handle user inputs well.

Let’s understand this with an example. This is a vulnerable logic form of an application:

SELECT * FROM users WHERE username = ' " + userInput + " ' AND password = ' " + passwordInput + " ';

Suppose an attacker inputs these commands to change the logic:

Username: ‘admin’ - -

Password: anything

The query now becomes:

SELECT * FROM users WHERE username = 'admin’ - -’ AND password = 'anything';

When you use ‘- -’ in an SQL command, it means you are using a comment operator to ignore everything that follows it. It allows the attacker to log in as the ‘admin’ user and proceed without entering the password. Result? They gain unauthorized access to the app’s database and execute their malicious intent.

7 Types of SQL Injection Attacks

SQL injection attacks are of different types, and knowing them helps you understand the risks of each one of them. It also prepares you to face SQL injection attacks head-on, understand their impacts, and the best way to mitigate them.

1. Classic SQL Injection Attack

In classic SQL injection, the hacker inserts malicious SQL commands directly into user input fields interacting with an app’s database. Attackers can now manipulate the input fields and change the structure of an SQL query to access the application and data without authorization.

In this SQLi type, the hacker’s communication channel is the same for executing the attack and obtaining the output. This is why it’s also called in-band SQL injection. Classic SQL injection attacks are easy and faster to execute as the attackers get to see the immediate results of the changes they make.

Example: A cyber attacker inputs an SQL statement into the search field of an app or site. The output of the statement is also displayed on the same webpage.

How It Works

To carry out a classic or in-band SQL injection attack, the attacker finds and exploits poorly created SQL queries of an application. They insert malicious SQL statements into input fields to alter the original logic of the query. And when they are successful at this, they can:

• Bypass authentication to gain access to the application
• Manipulate or steal confidential information
• Control administrative operations, such as changing/deleting records, creating new users, extending access privileges, making malicious backdoors for persistent access, etc.

How to Detect and Prevent Classical SQLi

Detection: To detect a classic SQL injection attack, look for suspicious or unusual app activities and signs that could indicate the presence of a classic SQLi attack.

• Abnormal app behavior: Unusual or abnormal behavior in the app, such as unauthorized modifications to records, records added/deleted, sudden data leaks, attempts to break authentication, etc., could be due to an attacker.
• Unexpected errors: If an app returns database errors, such as invalid SQL statements, syntax errors, etc., someone could be altering the app’s query logic.
• Suspicious SQL commands: If you find suspicious SQL commands in your application and database logs, this could be SQLi. Look for SQL statements with special characters, such as UNION SELECT, ‘  OR  ’1’ = ‘1’ to detect SQLi attacks.
• Scanners: Use cybersecurity tools, such as automated vulnerability scanners to detect SQL injection vulnerabilities.

Prevention: To prevent classic SQL injection attacks, take precautionary measures to remove vulnerable queries and other elements from your app. Some tips to prevent SQLi attacks:

• Sanitize and validate your inputs: Use secure libraries in your commands and avoid special characters, such as ‘  OR ‘1’ = ‘1’. Try whitelisting expected characters and reject unexpected characters to validate your inputs.

• Use parameterized queries: Use parameterized queries (eg. func(username, password) ) to separate your SQL query code and user input data, instead of concatenating user input into your SQL queries.

• Least privilege access: Allow a minimum amount of access permission to users and accounts, enough to complete their tasks.
• Use WAFs: Use web application firewalls (WAFs) to filter different types of SQL injection and block them before they get to your app database.
• Don’t expose error messages: Try not to expose database errors to end users in detail as attackers could be one of them. With this information, anyone may plan attacks anytime soon.
• Patches and audits: Carry out security audits periodically to find and fix vulnerabilities faster. Keep your database updated.

2. Blind SQL Injection Attack

A blind SQL injection attack occurs when the attacker injects malicious SQL commands into database fields “blindly,” meaning without directly obtaining the output of the command from the application, unlike classic SQLi. Instead, they look for indirect clues, such as HTTP responses, response times, app behavior, etc., to infer the result of the command. This is why they are also called inferential SQL injection. It is of two types – time-based SQLi and boolean/content-based SQLi.

Example: A hacker may inject conditional statements to check if the database contains a specific piece of information based on how the app responds.

How It Works

Blind SQLi attacks are definitely dangerous but not so common since they take quite a while to succeed. Since the app/site doesn’t reveal/transfer data to the hacker, the hacker sends harmful payloads to the database to learn the outputs themselves. They craft SQL queries to modify app behavior. After injecting the command, they observe how the app responds to the command to extract information.

How to Detect and Prevent Blind SQLi

Detection: Detecting blind SQL injections can be difficult as they show no error warnings, unlike classic SQLi. But there are ways to detect them:

• Monitor logs: Set up security monitoring systems to track application logs. Review your database to detect queries that seem unusual or suspicious and investigate them immediately.
• Check app behavior: If the app slows down suddenly or returns unexpected responses for different patterns of queries, there could be a blind SQLi.
• IDS: Intrusion detection systems (IDS) is a security solution to flag suspicious queries and validate them with deeper investigation.
• Automated scanners: Use automated vulnerability scanners to identify the presence of blind SQL injections in your app queries.

Prevention: Finding and fixing blind SQLi are important, so no one can tamper with your database queries and gain sensitive data. The following measures should help you prevent them:

• Prepared statements/parameterized queries: Treat user input as data, instead of just code. Add parameters in queries to separate user input values from SQL code.
• Error handling: When you detect errors in your database, don’t expose them to the public just yet. First, find the fix and secure your database, so hackers don’t get to the vulnerability before you patch it.
• Restrict access: Limit access privileges by enforcing policies, such as least privilege access, zero trust, and role-based access controls to prevent unauthorized access.
• Continuous monitoring: Monitor your application and database for threats and fix them before they become an SQL injection attack.

3. Time-Based Blind SQL Injection

Time-based blind SQL injection is a type of blind/inferential SQL injection. The attacker manipulates an app’s queries to cause delays in response deliberately. They depend on the app response time to decide whether their query is valid or invalid.

Example: A hacker sends an SQL query commanding a delay in response if the name “Jon” exists in the database. If the app delays in sending the response, the query is true.

How it works

In this method, the hacker sends an SQL statement to make the target database execute a time-intensive task or wait for a few seconds to respond. Next, the hacker observes how much time (in seconds) the app takes to respond to the query to determine if the query is true or false.

If the app responds immediately, the query is false and if it responds after waiting for a few seconds, the query is true.

How to Detect and Prevent Time-based Blind SQLi

Detection: To detect time-based blind SQL injection, use the same methods that we discussed in blind SQL injection. Let’s summarize them:

• Analyze response times: Send different SQL queries to the database to analyze their response times. Significant delays could indicate a time-based blind SQLi present in the code logic.
• Check logs: Check the app logs to detect signs of suspicious activities or unexpected delays.
• Behavior analytics: Track app behavior using anomaly detection tools. These will flag abnormal slowdowns and responses that indicate a vulnerability.
• Vulnerability scanners: Scan your application and database for SQLi vulnerabilities and resolve them immediately before they convert into attacks.

Prevention: Time-based blind injections harm your organization by stealing confidential data and compromising systems. Here are some tips to prevent them:

• Validate inputs: Keep database inputs sanitized by creating an allowlist of expected inputs while rejecting unexpected ones or special characters.
• Parameterized queries: Use parameterized queries (eg. function (a,b)) to separate user data and code and prevent hackers from exploiting your database queries.
• Test regularly: Conduct vulnerability assessments and penetration testing on your application regularly to detect and remove vulnerabilities.
• Update: Keep your application and database updated to their latest versions to ensure you use secure programs, free of bugs and errors.
• Limit access: Restrict access privileges so that only authorized people get to access sensitive data.
• Use advanced tools: Use advanced security tools, such as vulnerability scanners, powerful WAFs, and intrusion prevention systems (IPS) to prevent threats.

4. Error-Based SQL Injection

Error-based SQL injection is a type of classic/in-band SQL injection on applications and databases. It focuses on finding and exploiting error messages to determine the database details. Although error messages are handy for understanding the errors in a database when you are creating a web page or application, hide or get rid of them after production.

How it Works

A malicious actor inputs an SQL command that generates error messages intentionally from the database server. This lets them gain knowledge about the structure of the target database. They can also determine data values, column names, and table names with this method.

How to Detect and Prevent Error-Based SQLi

Detection: To detect error-based SQL injections, resolve them immediately, and limit the damages. Consider these tips:

• Unexpected error messages: If you enter a query into the database and you see unexpected error messages, it could signal an SQLi attack.
• Suspicious logs: Check whether the application and database have any suspicious logs or unauthorized activities.
• Scan for vulnerabilities: Scan your application frequently for SQLi vulnerabilities using automated tools to save time.
• Penetration testing: Run penetration testing on your applications to reveal security loopholes like a hacker does.

Prevention: Prevent error-based SQLi attacks from harming your organization in terms of finances, reputation, and customer trust with these tips:

• Disable error messages: Avoid revealing error messages to end users in detail. Attackers can use this weakness to carry out an SQLi attack. Try disabling error messages after an application or site is live. If you strictly need to, configure your app to display generic details.
• Log error messages safely: You can use a file to log error messages in it. Now, enforce access restrictions to this file to prevent it from falling into the wrong hands.
• Use WAFs: Use a web application firewall to block malicious SQL injection and prevent them from harming your database.
• Audit and update: Always keep your applications up-to-date with the latest version to prevent attackers from exploiting security vulnerabilities. You must also run periodic audits to find and fix hidden weak links.

5. Union-Based SQL Injection

Union-based SQL injections unite the outputs of multiple queries to form a single output using the SQL command – UNION. This merged output now is returned as an HTTP response, which is used to retrieve data from different tables under the same database. Hackers use this data to attack your database and application.

Compared to error-based SQLi, union-based SQLi is more common and difficult to fight. This is why you need stronger security solutions and strategies to beat it.

How it Works

First, an intruder tries identifying how many columns are there in the target database query. Until they see an error, the intruder keeps submitting different variations of this command to find the column count:

• ORDER BY 1 - - 

• ORDER BY 2 - - 

• ORDER BY n - -

Next, they use the UNION command to merge multiple SELECT statements into one to obtain more database information.

How to Detect and Prevent Union-Based SQLi

Detection: Detecting a union-based SQL injection lets you combat and neutralize the threat before it becomes a full-blown attack. Here’s how to detect union-based SQLi:

• Analyze logs: Check your database logs to find suspicious SQL commands, especially UNION statements. If you find one, start a deep investigation immediately.
• Track page behavior: Monitor your web page/application for unusual behavior, such as displaying additional details that you did not request.
• Test: Conduct security tests, such as penetration testing, on your application to understand if it has SQLi vulnerabilities. It tells you how secure your app is by acting like an attacker.

Prevention: If you want to reduce the chances of union-based SQL injections, prevent them with these methods:

• Use prepared statements: Secure your code from hackers with prepared statements or parameterized queries  (eg. function(username, password)).
• Restrict database permissions: Limit people from accessing your database to prevent them from inserting ‘UNION’ queries.
• Validate inputs: Whitelist special characters and avoid suspicious ones to reduce the chances of hackers manipulating your codes.
• Use advanced tools: Use tools, such as vulnerability scanners, IDP/IPS, and WAFs to block SQL injection from reaching your application’s database.

6. Out-of-Band SQL Injection

Out-of-band SQL injection is not so common, but when it happens, it can impact your organization’s reputation and finances.

Unlike in-band/classical SQL injection, hackers use different channels to attack your database and get the result. They use this attack when they cannot deploy an in-band or inferential SQL attack. It could be due to slower or unstable database servers or certain features in the app.

How it Works

Hackers carry out out-of-band SQLi in secure IT environments where the applications are configured to block direct database responses. In this scenario, they are unable to retrieve data using the same channel they used to insert malicious code. So, they opt for an external, more sophisticated communication mode instead, such as HTTP or DNS requests to fetch data from less secure databases.

When an attacker injects harmful SQL commands into the database, it triggers or forces the database to connect to an external server that they have control over. This way, the attacker retrieves sensitive information such as user/system credentials, and analyzes and exploits it to control the database.

How to Detect and Prevent Out-of-Band SQLi

Detection: To detect out-of-band SQLi to be able to fix them before any compromise happens, consider the following ways:

• Monitor external traffic: Since out-of-band SQLi requires an external connection, monitor your outbound traffic, such as HTTP or DNS requests. It helps you catch unusual traffic that could be an out-of-band SQLi.
• Log database: Frequently check your database logs to spot suspicious quests to known or external servers.
• IDS: Use intrusion detection systems (IDS) to detect the presence of unauthorized access attempts to an external server.

Prevention: Here are some tips to consider to prevent out-of-band SQL injections:

• Use allowlists: Create an allowlist of authorized IP addresses and domains that your data must communicate with, rejecting all others. This restricts your database from connecting with malicious servers and exposing data.
• Disable external communications: Restrict access to your database, so external URLs, file systems, network connections, etc., cannot interact with it.
• Use PoLP: Limit database access permissions by applying the principle of least privilege (PoLP). It reduces the chance of malicious actors executing functions/commands, such as ‘load_file’.

7. Second-Order SQL Injection

Second-order SQL injection is an advanced cyber threat where an attacker deploys and stores a malicious SQL-based payload in a database. This payload would not execute immediately after. Instead, if a different SQL query processes this stored payload, the payload will be triggered.

Unlike in-band SQLi, which can manipulate commands in real time, a second-order SQL injection exploits user inputs stored in the database.

How it Works

First, the attacker will inject the SQL payload into an app’s field that saves data in its database, such as user registration, profile updates, comments, etc. Next, the payload will sit there as if it were dormant, doing no harm, operation disruptions, or errors. This allows attackers to gain unauthorized access to databases, manipulate data, and harm your business.

How to Detect and Prevent Second-Order SQLi

Detection: Here are some of the ways to detect second-order SQL injection, so you can prioritize and remediate them faster:

• Code audits: Audit your application logic from time to time to identify sections where SQL queries have user inputs stored from the database.
• Monitor your database: Monitor the database continuously to find unauthorized or unexpected SQL commands stored or being executed.
• Check interactions: Use behavior analysis tools to check if the database is interacting with external or unknown URLs and file systems.

Prevention: Consider these methods to prevent second-order SQLi attacks and avoid reputation and financial losses:

• Sanitize inputs: Sanitize your inputs at each stage, especially at the entry points, and before reusing them. It will help you detect and remove the malicious code sitting in your database.
• Test regularly: Perform regular testing on your application, such as penetration testing, vulnerability assessments, compromise assessments, etc., to find, neutralize, and mitigate threats.
• Limit access: Use access controls, such as the principle of least access, zero trust, and role-based access, to restrict users from accessing your database.

Real-World Examples of SQL Injection Attacks

Let’s talk about two of the infamous SQLi attacks in history that had disastrous consequences:

• Equifax data breach: Equifax, a credit reporting company, faced an SQLi attack in 2017. Attackers found and exploited a less secure web app and executed malicious SQL queries to gain unauthorized access to confidential customer information.

This exposed 143 million customers’ data including their names, birthdays, addresses, and social security numbers. The company could not detect the attack for months and when it did, it was too late. Equifax had to pay more than $1.4 billion in fines and settlements.

• Yahoo: Yahoo suffered a massive SQLi attack in 2014 where attackers injected malicious code into its vulnerable apps. With this attempt, the attackers successfully gained 500 million accounts of Yahoo’s users.

With this data breach, attackers compromised usernames, passwords, security questions, and more. As a result, Yahoo’s valuation went down, which affected Yahoo during its acquisition by Verizon. It once had a $100 billion valuation, but Yahoo had to sell it for only $4.83 billion.

How to Prevent SQL Injection Attacks?

A single application with malicious SQL injection is enough to allow cybercriminals to access a company’s database and confidential data. This will lead to financial and reputational damage. But you can protect your applications from different types of SQL injection attacks by following these tips:

• Avoid embedding user inputs directly in SQL queries. Instead, use limited queries and prepared statements to differentiate code from data. This will execute queries securely and prevent SQLi attacks.
• Restrict your SQL database access based on roles and permissions. Allow users minimum privileges, necessary to perform actions to reduce the impact of the breach.
• Use stored procedures to control the interaction between queries and the database to reduce direct exposure to SQL commands from the user inputs.
• Execute strict validation rules to use only expected data formats to block malicious SQL code from entering your system.
• Regularly update applications and check security patching to minimize security risks.
• Use advanced cybersecurity tools to detect and block SQLi attempts before they enter your database. The tools monitor unusual database queries, query patterns, and logging access to eliminate risks.

How Can SentinelOne Help?

SentinelOne is a leading cybersecurity platform in the world with advanced capabilities, such as AI and ML algorithms, behavior analysis, and tools and techniques to help you detect, neutralize, and prevent common types of SQL injections.

No matter what type of SQL injection is prevalent in your business or industry, SentinelOne can combat it to protect your applications and confidential data. Let’s discuss SentinelOne’s capabilities:

• Singularity Cloud Security: This powerful CNAPP solution safeguards your applications and cloud resources, from development to runtime. It comes with real-time threat detection and response, threat intelligence, hyper automation, infrastructure-as-code scanning, and more.
• Singularity Cloud Workload Security: It uses AI to protect your cloud environments by detecting and remediating SQL injections and other threats in real time. It provides full forensics, auto-scaling, Snyk integration, etc.
• Singularity Endpoint: Get enterprise-grade security for your endpoints, mobile devices, and servers from SQLi attacks. It offers real-time EDR, attack surface management, quick rollbacks, and other features.

SentinelOne offers other tools, such as Singularity Data Lake, Singularity Identity, AI-SIEM, and Purple AI, to provide superior protection against SQLi attacks.

Get a demo to see SentinelOne’s offerings in action.

Conclusion

Different types of SQL injection attacks target web applications that use SQL databases to gain unauthorized access. Cybercriminals often succeed because of the vulnerabilities in applications, such as unsanitized user inputs. Once they get access, they can steal customer information, confidential company data, financial records, etc., and harm your business’ reputation.

The key preventive measures you need to implement include input validation, continuous monitoring using advanced security tools, prepared statements, limited access, and more. Attackers always refine their strategies to gain access, so you must stay ahead using penetration testing, threat detection, and regular security audits.

Don’t wait for a cybercriminal to take action first. Instead, be the first to secure your applications from different types of SQL injection attacks using SentinelOne’s reliable, AI-powered, and powerful cybersecurity tools. Take a demo to know more.

FAQs

1. How do microservices architectures complicate SQL Injection Prevention?

Microservices split application logic into numerous standalone services, and each may use its own database. Decentralization can lead to inconsistent input validation practices and more attack channels. Implementing uniform security controls, rigorous logging, and quality communication monitoring among services is paramount.

A bug in one microservice can become amplified, so robust, service-level SQL injection defenses are vital to protect the entire system.

2. What unusual testing techniques can expose concealed SQL Injection Vulnerabilities?

In addition to common penetration testing, applying fuzz testing, mutation analysis, and artificial intelligence-driven anomaly detection can detect subtle SQL injection vulnerabilities. These techniques mimic disparate and unpredictable inputs, revealing flaws in query logic that common tests cannot detect.

By integrating these advanced techniques, organizations can improve detection and repair of elusive types of SQL injection attacks before attackers discover and exploit them.

3. How does integrating threat intelligence make SQL Injection Detection better?

Threat intelligence integration makes SQL injection detection better through the correlation of global attack trends and new techniques with real-time query monitoring. This proactive approach allows security systems to detect unusual query patterns indicative of SQL injection attempts.

Real-time threat feed updates allow developers and security personnel to enhance input sanitization and response methods, effectively eliminating potential vulnerabilities in dynamic environments.

4. What dangers do legacy databases present in the context of SQL Injection?

Legacy databases lack modern security functionalities, and they are susceptible to SQL injection by the nature of out-of-date input sanitization and weak access controls. Built-in architectural shortcomings create exploitable vulnerabilities, permitting attackers to quickly manipulate queries and gain access to sensitive information.

Stopping these threats requires rigid patch management, enhanced monitoring, and the addition of new security controls to defeat advanced SQL injection attacks.

5. How are new NoSQL injection attacks different from Traditional SQL Injection?

While traditional SQL injection is aimed at relational, structured databases, NoSQL injections are aimed at vulnerabilities in document-oriented, unstructured data stores. Attackers exploit native query languages of the NoSQL databases, frequently through the absence of input validation and non-compliant security procedures.

Mitigation for these attacks includes advanced solutions like robust sanitization, parameterized queries, and constant monitoring to sufficiently secure evolving NoSQL environments.