What is SQL Injection? SQLI Prevention and Mitigation

SQL Injection Prevention

What is SQL Injection?

SQL Injection is a kind of cyber-attack based on targeted databases by submitting malicious SQL code instead of input on web application fields.

This code is created with the purpose of affecting the structure of the database query that the application interacts with the backend database, thus making it vulnerable to hackers who can breach its security, modify data or carry out malicious actions.

Generally, SQL injection is done through login forms, search boxes, or any user-controlled filter fields, in which a web application interacts with a backend database through SQL queries.

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Using the unprepared handling of application inputs as their point of entry, the attackers can bypass authentication, extract private information such as usernames and passwords, or worse, gain total control of the whole database server.

Speaking of SQL Injection attacks, these attacks present a huge threat to web applications that use SQL databases for storing and retrieving data; otherwise, a big potential damage may follow.

Types of SQL injection

There are several types of SQL injection attacks, each exploiting different vulnerabilities in web applications and database servers:

1. Classic SQL Injection

This is the most general type of SQL injection vulnerability. Attackers normally embed the malicious SQL code within a few input fields, including login areas or search query boxes, and sometimes in the URL parameters of a web application.

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Injected SQL code opens the database to SQL injection, which can be used to tamper with the regular SQL query processed by the database server to steal sensitive data, such as usernames, passwords, or any other private data.

2. Blind SQL Injection

In this SQL injection attack, attackers cannot see direct feedback from the application on whether the injected SQL queries they sent are successful. On the contrary, they exploit methodologies like logical and time-based blind insertion to guess the database parameters remotely.

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By getting a response from the application, the attacker can check which expression is true and false which eventually leads to the information extracting or other malicious purposes.

3.     Error-based SQL Injection

Error-based SQL injection attacks work by taking advantage of the error messages that the database server sends when it faces malformed SQL queries.

Attackers use SQL injection attacks that involve SQL code copies with the aim of triggering database errors and then dissecting received messages to figure out database schema or content.

This kind of data may assist attackers in improving their assault strategy and identifying individuals that they can proceed to attack.

4. Union-based SQL Injection

Union-based SQL injection attacks use UNION statements in SQL to return the result set of two or more SELECT statements.

Injected by an adversary, a UNION SELECT statement is run by the database server, executing additional queries and returning them together with the original query results.

The hacker is able to snoop on other database tables that might not have been directly accessible through the application.

5. Time-based SQL Injection

Time-based SQL injection attacks expose the database functions that are executed with the help of the database server-specifics, such as the delay feature of the query execution.

Attackers insert SQL code that captures the database server response time when the injected condition is true, they can in this way make a query by the type of information they need from the database.

Time elapsed in receiving different inputs to or from the server is attacked which in turn leads to extracting data or performing other malicious actions.

6. Out-of-Band SQL Injection

Unlike In-Band SQL injections, which use web-based techniques to attack the database servers, Out-of-Band SQL injections leverage the ability of the server to have an external system connection.

Attackers could introduce SQL code that results in off-network requests that, in turn, allow them on the remote systems to communicate with the attacker or carry away the data.

This method is especially effective when the most expeditious communication channel with the compromised system gets disconnected or blocked.

How & Why is an SQL Injection Attack Performed?

SQL injection attacks are achieved by accepting unauthorized SQL code into ordinary SQL statements through the web application and using the data in SQL databases with the intention of updating information without permission.

The vulnerabilities of such platforms could eclipse intruders with unauthorized access of sensitive information and even to the extent of gaining complete control of attacked websites, applications, and database servers.

SQL injection attacks do not only happen in one way. For example, executing commands on the database server, retrieving data based on errors, or manipulating query logic.

To block SQL injection attacks, the secure programming functions to be used should be parameterized queries and stored procedures.

The software and components must be kept in an updated version, the input to be validated as an allow list is suggested, the Principle of Least Privilege needs to be implemented, and the web application firewalls to filter the web request must also be used.

Biggest Example of an SQL Injection Attack

The Equifax data breach that happened in 2017 is one of the most prominent SQL injection attacks. Attackers managed to take advantage of the security flaw in Equifax’s website software, which was Apache Struts, which was not downloaded with the latest security updates.

This opening offered the attackers a chance to insert malevolent SQL commands into Equifax’s database.

Thus, the hackers that were able to use this vulnerability got unauthorized access to about 147 million people’s sensitive personal information such as names, birth dates, addresses, Social Security numbers, and in some cases, even driver’s licenses.

The culprits obtained hundreds of terabytes of information over six weeks and had no idea. The impact of the Equifax breach was extensive, with many individuals experiencing identity theft or financial fraud as a consequence.

In addition to substantial financial and brand damage, Equifax faced multiple lawsuits, investigations by regulatory bodies, and loss of the confidence of customers.

This case shares the lesson of the necessity to have sound security measures to prevent SQL injection attacks, including regularly updated software with the most recent security patches, strategic coding practices, and stricter controls for authorized access to sensitive databases

What is the Impact of a Successful SQL Injection Attack?

The impact of a successful SQL injection attack can be severe and wide-ranging:

Data Breach:

Pirates may use unpermitted methods such as Mechanical Access, Social Engineering, and SQL Injection to breach databases and thereby leak restricted information like personal details, financial data, intellectual property, and others.

Identity Theft:

Stolen personal data, including names, SSNs, and credit card details, may end up being used by identity thieves for fraudulent purposes and causing monetary damages as well as harm to your credit score

Financial Losses:

Cybercrime greatly affects the financial status of organizations as they might suffer a pecuniary loss due to theft of financial data, fraudulent transactions, regulatory penalties as well as legal costs involved in solving the problem.

Reputation Damage:

An SQL injection attack can lead to such a data breach, which can ruin the reputability of an organization and harm clients’ trust in it.

As a result, companies can witness a drop in their sales, attracting unwanted negative coverage and tarnishing reputation in the long run.

Organizations may be on the hook to pay settlements or lose revenue if they get sued by affected individuals or fined by regulators for non-compliance to data protection laws (for example, the GDPR or CCPA). Also, the organizations could be investigated by the regulatory authorities.

Operational Disruption:

In most cases, tampering with a SQL injection involves disruption of normal business operations that necessitates resources such as investigation of the entrance, ameliorating influence, and putting security changes in motion to prevent recurrence.

Loss of Competitive Advantage:

The worst-case scenario would be what happens when confidential information or trade secrets are revealed. It may be that another and more advantageous competitor would emerge after they get access to your privileged intellectual property.

How to Detect SQL Injection Vulnerabilities?

SQL injection detection proves to be a mix of both automated tools and manual testing. Here are some methods:

Automated Scanners:

Make use of those exclusive tools such as SQLMap, Acunetix, or OWASP ZAP for scanning websites for the most typical SQL injection problem.

We can tell the change by tools operating SQL injection defect exploring methods with reporting results about vulnerabilities of the application wherever they are detectable.

Input Validation:

Adopt strict input validation and sanitization processes to guarantee that the users’ data is well-structured without carrying any malicious SQL expressions.

Take advantage of parameterized queries or prepared statements to keep out SQL injection attacks.

Error Handling:

Look carefully at error messages and the reactions of an application when data entered are played with.

Error handling is a critical aspect of web application development, particularly when dealing with user input and database interactions.

In the context of SQL injection vulnerabilities, proper error handling can help prevent attackers from exploiting potential vulnerabilities.

Database Logs:

Keep a check on database logs for searches that are suspicious or do not follow the standard search pattern for SQL queries, which may have SQL injection keywords or have some unusual search patterns.

Keep records accordingly and review access logs in order to detect unauthorized access attempts.

Security Headers:

It is important to install security headers, for instance, Content Security Policy (CSP) and the X-XSS-Protection header, in order to prevent SQL injection and other injection-based attacks by issuing the browser’s behaviors and enforcing security policies.

Code Review:

Conduct in-depth code reviews of application source code, where you will be focusing on an area allowing users to input data, process such inputs, and emit it (i.e., from form submissions, URL parameters, and HTTP headers).

Figure out situations when an injection is done by just sticking input directly to SQL query without proper validation or sanitization.

Penetration Testing:

Conduct manual penetration testing or engage 3rd party security testing firms to identify SQL injection vulnerabilities, employing manual testing techniques that include fuzzing, input manipulations, and black-box testing.

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Web Application Firewall (WAF):

Distribute WAF that will be able to scan incoming HTTP traffic for requests suggesting SQL injection and block them.

WAFs can offer an additional barrier in front of any SQL injection techniques, be they known or completely unknown.

How to Review Code for  SQL Injection Vulnerabilities?

SQL injection vulnerabilities are often caused by improper user input handling and query buildup. Accordingly, the code review process should focus on how user input is checked before being converted into an SQL query.

Here’s a checklist for reviewing code to identify and mitigate SQL injection vulnerabilities:

Input Validation:

Make sure that the user input is safe enough for SQL queries by checking what the validating and sanitizing methods are called.

Verify that source data is properly formatted and the length is validated from validation rules, and also the sensitive characters, if any, should be removed or at least properly sanitized to prevent harmful SQL syntax’s implementation.

Parameterized Queries:

Seek out the practice of parameterized queries or prepared statements rather than just putting user input directly to SQL queries concatenated.

In other words, parameters in Query mark SQL code away from the user data, preventing SQL injection attacks that are blessed with any of the user’s input as source code.

Escape Characters:

Double-check whether basic escape characters are used correctly to keep the information safe from dangerous user inputs.

Escape of special characters as single quotes (‘), double quotes (“), and semicolons (;) so it prevents SQL injections from becoming a part of SQL syntax rather than an element of SQL syntax.

Stored Procedures:

Take a look at the prepackaged stored procedures for core business processes and control access to DBMS.

Saved procedures are able to reduce SQL injection vulnerability as an implicit way to deal with the database it provides with a fixed interface, giving a reduced possibility of facing direct SQL injection attacks.

Input Sanitization Libraries:

Check if the application is making use of libraries or frameworks that sanitize user input on its own without you having to add any code to sanitize them before you use them in SQL queries.

Such libraries help to ensure the same input sanitization techniques across the application, thereby preventing any error bugs related to human factors.

Database Permissions:

Ensure the application database user account has permissions that satisfy only the small subset of what is required for the software to perform as it is supposed to.

Circumscribing the roles assigned to the database itself may limit the result of the SQL injection to the hacker’s lack of authorization to specify or modify malicious commands and to access sensitive data.

Code Review Tools:

Using automated code review tools or static analysis tools that already have the knowledge of identifying the SQL injection vulnerabilities is more effective.

These tools might allow finding possible weaknesses and they can offer remediations explaining how to repair them during code reviewing.

Security Best Practices:

Promote security compliance through least privilege access control, secure coding standards, and continuous security awareness programs in a bid to keep up with the evolving security threats.

Abiding by a security-conscious team culture can minimize the risk of SQL injection attacks and other potential security lapses.

How to Prevent SQL INJECTION Attacks & Vulnerabilities?

Preventing SQL injection attacks involves using parameterized queries, input validation, and proper user authentication:

Parameterized Queries:

Deploy input parameterized queries or prepared statements in your code to make the boundary between data and SQL logic more obvious. The fact that it disables malicious input dialogues from changing SQL queries is what this does.

Input Validation:

Take responsibility for validating and sanitizing input on both server and client contexts. Make sure that just the correct data types and formats are received, and any input that doesn’t match the established standard of patterns has to be rejected.

Least Privilege Principle:

Minimize privilege assignments of the accounts that are created for the databases. Restricting those resources and operations to only those needed for a usual function of any business.

Escape Special Characters:

If you are not utilizing parameterized queries allow for escaping special characters such as quotes (‘), semicolons (;), and dashes ( – ) before executing your SQL query.

Update Regularly:

Don’t forget to always keep your DBMS version updated with the newest security patch and data to handle any security risk detected.

Use Stored Procedures:

Stored procedures are well-designed and invoke processes for executions from within the database that reduce the level of access that can be performed against the database.

By incorporating thin barriers (row-level security), it embodies a supplemental defense firewall that does not permit direct access to tables.

Implement Web Application Firewall (WAF):

Utilize a WAF to protect your web app from HTTP traffic that travels from the internet to your web app through the filter and monitor modes. It can detect and do the order of SQL injection injections.

Input Parameterization:

Make sure both input validation and parameterization are strict in order to accept data types and formats with only expected values.

Error Handling:

While the disclosure of error messages in human-readable form may be disruptive, it is advisable to keep messages as abstract as possible, especially in production systems.

Instead of displaying detailed error messages for administrators and generic error messages for users only, it is advisable to put canned error messages for users so that they can avoid sabotage with technical words.

Best Practices to Protect Your Database from SQL Injection

In order to protect your database from SQL injection attacks, you must follow these best practices:

Input Validation and Sanitization:

Every time, validate user input and remove incorrect characters before adding these inputs to SQL queries. Do whitelisting to allow the input only of expected values and reject everything else.

Sanitize the input by running special characters or using parameterized queries to make them separate from the SQL commands.

Parameterized Queries/Prepared Statements:

Implement the parameterized queries or prepared statements presented by the database programming interface you are using.

These support systems create a barrier in which SQL commands would not be submitted along with the user input, making it impossible for an intruder to inject malicious SQL commands.

Least Privilege Principle:

The least privilege is trustworthiness. Therefore, restrict user permissions to the minimum required for their assignments. Don’t employ a highly privileged database username to obtain application access ability.

Recommended: What Is Privilege Escalation? How to Detect and Prevent Privilege Escalation Attacks in Windows

Limit the ability of the database user to the required objects and operations by their roles in the database server.

Stored Procedures:

Encapsulate business logic and access control in the stored procedures. Stored procedures are the best way to control your database.

Scheduled procedures may help enhance SQL injection attacks as they are, by definition, prepared in advance, hence reducing the chance of direct SQL injection problems.

Database Firewalls and Intrusion Detection Systems:

Deploy database firewalls and intrusion detection systems (IDS) to filter suspect SQL traffic. This will shield the database server from penetrations and other attacks.

They may spot suspicious SQL queries that the hackers tend to use and may block them promptly. Besides that, this makes it harder for hackers to penetrate your system.

Regular Security Patching:

Update the DBMS and your software frequently, and make sure that you install all the relevant security patches so that the latest security vulnerabilities can be fixed.

Database software vulnerabilities may be used as an entry point for unauthorized access or the execution of malicious SQL commands.

Secure Configuration:

Apply secure configuration to your database server by disabling all unneeded services and ports, as well as the unnecessary server features.

Follow security guidelines, as recommended by database vendors, in order to fortify your database server and secure it against attacks.

Monitoring and Logging:

Enforce strong logging and monitoring functions in order to track database operations and perform detection of suspicious activities which systems consider SQL injection.

Follow the database logs, audit trails, and security events in order to get a timely response to security incidents.


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Janki Mehta

Janki Mehta

Janki Mehta is a Cyber-Security Enthusiast who constantly updates herself with new advancements in the Web/Cyber Security niche. Along with theoretical knowledge, she also implements her practical expertise in day-to-day tasks and helps others to protect themselves from threats.

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