SQL injection is one of the most dreaded forms of cyber attacks because of the devastating and far-reaching effects hackers can leave behind when they use the method.

In this article, we will explore what an SQL injection is, how it is performed, what its different forms are, and how you can prevent an SQL attack. Read on!

What is an SQL Injection?

SQL injection is a form of cyber attack that allows the hacker to inject a malicious SQL code into an application or program, and remotely view or modify databases.

SQL stands for Structured Query Language and is a computer language that can manage or manipulate data in a database. The actions that a hacker can perform on a database server with an SQL query include deleting data sets, modifying data, bypassing authentication, stealing data, running codes, running code, and actions like gaining root access to the whole system.

How Is an SQL Injection Attack Performed

If a website or a program uses an SQL database, it can be subject to an SQL attack in case of any SQL injection vulnerabilities. Once an attacker identifies a vulnerability in a web application or webpage, they can initiate an SQL injection. Once the SQL is injected, the user input in the web application directly works in the form of an SQL Query.

SQL injections allow a hacker to skip the authentication step that a normal user would need to input to access sensitive data within their accounts. Once a hacker has skipped the authentication part, they have access to all the information and can get access by issuing queries.

SQL queries that have been injected into a web application can execute SQL commands such as creating updates, recording removal, data retrieval, and more, without any permission required in most cases. Furthermore, a hacker can use SQL injection to know the layout and construction of the database.

Since most databases support SQL statements, the attacks have become more frequent as there are different types of SQL injections.

Types of SQL Injection Attacks

1) In-Band SQL Injection

This is a type of SQL attack where the hacker uses the same communication channel to issue a query when launching an attack and to gather the results. The in-band SQL injection is the most common form of SQL attack.

There are two forms of in-band SQL injection;

a) Error-Based SQL Injection

In this form of attack, the hacker focuses on finding out the structure of the database. The hacker relies on error messages sent by the database server to enumerate an entire database.

Error messages can be deleted to prevent SQL injection attacks of this kind. Furthermore, the messages can be stored in restricted files to prevent attacks.

b) Union-Based Attack

Union-based SQL Injection attacks leverage the UNION SQL operator by combining the results of multiple SELECT statements into a single result. The result is then returned in the form of an HTTP response.

2) Out-of-Band SQL Injection

When an attacker is unable to get results through the same channel they used to send a query (as in in-band SQLi), they will use an out-of-band SQL injection. Furthermore, since the attacker can not depend on the server response, time-based inferential injection attacks are not an option for them.

For this attack to be possible, certain features have to be enabled on the target database used by a web application. The server should be able to create either a DNS or an HTTP request to enable data transfer.

3) Inferential SQL Injection

Inferential SQL injection is also known as a blind SQL injection. This is because the malicious user will not be able to see the results of the queries (as they would in the case of in-band injection attacks).

In this form of SQL injection, the attacker sends payloads to the server, then observes the web page or application response and the database server’s behavior. From this, the hacker can be able to deduce and reconstruct the database servers.

There are two types of inferential SQL injection attacks;

a) Boolean-based SQLi

Boolean-based SQL injections are also known as content-based blind SQL injection attacks. The attack relies on sending SQL queries to a database, forcing an application to return a different result. The result will depend on whether the query is TRUE or FALSE.

Based on the true or false query message, the attacker can choose their next form of action.

b) Time-Based Attack

Time-based SQL injection sends an SQL query that forces a to wait for a given period (in seconds) before sending a response. Based on the time taken before a response, the attacker can know whether the result is “true” or “false”.

While the attacker gets an HTTP result from this form of hacking, they do not have to depend on it.

4) Unsanitized Input

User input involves the use of characters like numbers or symbols. In some websites, the query string is not sanitized enough to reject certain queries, and hackers may take advantage of this to pull out sensitive data from such applications. Sanitization, or input validation, is the way to prevent this type of attack.

How to Prevent SQL Injection Attacks

a) Staff Training

When it comes to preventing cyber attacks, especially in an organization, the best place to start is to avoid negligence of any kind, as they might leave loopholes for an attack since hackers look for vulnerabilities in systems. Most of the time, negligence is based on human errors, and staff security awareness training can help mitigate the risk of an attack.

b) Use the Latest Versions

Using the latest versions of web applications, security patches, languages, and programs will reduce the chances of your sites getting hacked into.

c) Web Application Firewall

Firewalls filter out any malicious SQL queries, data, and attacks. Most firewalls have SQL injection defenses that catch any attempts to inject SQL into web applications.

d) Encryption

Any sensitive data should be encrypted with salted encryption hashes. Even if a hacker initiates a successful SQL injection attack, the data will not be of much help.

The data sets you should encrypt include passwords, connection strings, codes, card numbers, and other personal information that you would not leave open for anyone to see.

e) Limit Privileges and Access

Each SQL database should have the least amount of privileges. For example, if all a database requires is the SELECT statement, there is no need to have other statement privileges such as DELETE, INSERT, or UPDATE.

Furthermore, you can limit the access to the databases to only the necessary admin access. This reduces the number of activities and, in turn, the chances of a breach when no one else can gain unauthorized access.

f) Eliminate Shared Databases

SQL injection works by taking advantage of vulnerabilities, and many applications or websites sharing a single database increases the chances of an attack. Each web application has its database is the best way to go.

g) Avoid Displaying Error Messages

Attackers can use an error message to tell the structure of a database. If you hide or delete the error message, you could avert an attack.

h) Use Stored Procedures

Stored procedures are prepared statements and codes that are not used directly on the database by the user. Instead of direct execution of codes in a database, the application in which the procedure is stored activates the code and sends the result.

While stored procedures are used to avoid writing codes over and over again, it can reduce the chances of an SQL injection attack since the code is not executed in the database.

i) Deny Extended URLs

One method attackers use is to explore potential databases using extended URLs. Once you deny extended URLs you render this method obsolete.

j) Do Not Use Dynamic SQL

Hackers run malicious SQL statements on a vulnerable SQL server. To reduce the risk of the malicious code retrieving any information, the user input should not be placed directly on the SQL statement. Otherwise, the attacker can gain access once they have infiltrated the database.

k) Maintain Applications and Databases

Running penetration tests regularly on your databases will ensure you are on the safe side in case of an attack. You will be able to weed out any database errors during a penetration test. Statements like parameterized queries are easy to maintain, and hence you can make security updates often.

l) Monitor Database Communication

When you monitor communications, you can be able to tell when a malicious statement comes about. Through privileged access management and the use of tools like Security Incident and Event Monitoring(SIEM), you will be able to see the trends in your SQL databases.

Final Thoughts

SQL Injection vulnerability is one of the things hackers rely on most. To prevent SQL injection attacks, it is best to be on top of your cyber security matters at all times. The best way to go about this is to have to identify the threats and mitigate them before they happen by hiring cyber threat intelligence services.

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