SQL Injection is a common cyberattack that affects corporate databases of popular organizations. It is one of the most common cyberattacks that has a great potential to damage. Hackers use this technique particularly to damage databases of the target organizations. Before getting to the topic, it is required to understand what SQL is so that the concept is clear. So, let’s start with the basics of SQL.
What is SQL?
SQL is an acronym for Structured Query Language. It is a widely used programming language for managing various databases. To access, read, and manipulate data in various types of database systems like MySQL, Oracle, etc., SQL is needed. All web applications work only if they are connected to their databases and they cannot work without that connection. Web applications connect to their respective databases through SQL as it is used to access the information stored in the databases like user information, important files, sensitive data, etc. Therefore, it becomes a vital tool which links both databases and web applications. Web applications can be in the form of browsers, games, and various types of applications. They all have to be connected to their databases to perform their functions in a normal way. If they lose connectivity, they cannot perform their intended functions as expected.
What is SQL Injection?
When attackers abuse or hack the connection between web applications and their databases by introducing malware (using an SQL query), it is commonly called SQL injection. It is carried out by attackers by supplying SQL commands which are used as user-input variables in an attempt to make web applications execute their code on their databases. SQL injection attacks are the most common types of attacks that are carried out to create, delete or alter the information stored in database servers by inputting some SQL queries on web applications. Criminals or attackers can damage organizations by using SQL injection attacks and compromise the integrity and safety of their databases.
How are SQL Injection Attacks Launched?
It is a pretty obvious question that attackers launch this attack? It occurs when any untrusted user-supplied data is used on a web application and that particular data is used to create a SQL query dynamically that is executed by the respective database. Web applications which use ASP, JSP, PHP, and other older server-side scripting languages are more prone to such attacks but the applications using ASP.NET & J2EE scripting languages are less prone to those attacks due to better security and safety.
Consequences of an SQL Injection Attack
If any application is vulnerable to SQL injection attacks (it affects mainly applications that do not have strong user validation while logging in to the server), then attackers have the ability to influence and control the SQL that is used to communicate with the respective database thereby compromising the overall security and confidentiality of the information stored on the database server. The attack can help attackers modify, change or steal the information stored on the server like changing user passwords, user credentials, etc.
Possible threats of SQL injection attacks are
- Stealing of user information like passwords, sensitive data, etc.
- Unauthorized changes in user credentials.
- Create new user ids or delete existing user ids.
- Impersonate users or even the database administrator.
Types of SQL Injection Attacks
Basically, SQLi can be classified into three major categories:
- In-band SQLi: It is the most common type of SQL injection attack wherein hackers can easily exploit the database by using the same communication channel. It is also called Classic SQL injection as it is most prevalent.
- Inferential SQLi: It is not so common as in-band because hackers cannot see or exploit the database information easily but they can reconstruct the structure of the database based on the response received from it. It is also referred to as Blind SQL injection because hackers cannot see the results of their attacks.
- Out-of-band SQLi: It is not a common type of SQL injection technique wherein attackers are not able to use the same channel to attack and gather results. It is an alternative to Inferential time-based SQL injection when server responses are not stable which makes time-based SQL injection attack unreliable. It uses the ability of the server to deliver the results through HTTP or DNS requests.
In-band or Classic SQLi can be further classified into
- Error-based SQLi: This type of in-band SQL injection is most commonly used by attackers where it is possible to gather all the information on the database just by accessing the error message generated by the database server. The error-based SQL injection technique helps the hacker to get the essential information regarding the database without making much efforts as the error message sent by the database is used to enumerate the database entirely. The error messages should be blocked on a live website after undergoing the development phase as it enables hackers to steal the information stored on the server very easily.
- Union-based SQLi: This type of in-band SQL injection uses the UNION SQL operator to gather or collect information of two or more SELECT statements into one result which can be returned as a part of an HTTP response easily.
Inferential or Blind SQLi can be further classified into
- Content-based SQLi: This technique relies on sending an SQL query to the database that forces the application to return or send a different result depending on whether returns a TRUE or FALSE result. It is also called Boolean-based SQL injection as the content within the HTTP response depends on the result TRUE or FALSE and it is slower than other forms of attacks, especially on large databases.
- Time-based SQLi: In this attack, hackers send an SQL query which forces the database to wait for a specified amount of time, usually within seconds, before responding. The waiting time determines whether the result is TRUE or FALSE.
It is also a slower hacking technique when used for larger servers.
Real-time Examples of SQL Injection Attacks
- SQL injection attacks were used to hack Sony Pictures, HBGary, and PBS in 2011.
- Attackers used SQL Injection in an Adobe data breach to steal user information, names, and email addresses one of the databases a few years ago.
- SQL Injection was used at 7-Eleven retail chain to compromise their corporate systems. The attackers stole 130 million credit card numbers in this attack.
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