Understanding SQL Injection Attacks

Every day countless of web servers, as well as systems, are explored, scanned and attacked. Now the attacks have exceeded beyond worms and viruses. Particularly, vulnerable to hacker are a web application, web server security, application security software and entire website security. SQL injection is the most malicious hacking method. It is also referred as inference attack. The effectiveness and versatility of the SQL injection make it most preferred choice among the attackers.

In this attack, the hacker appends SQL query code as an input to a web form to gain access or alter the resources or data. 

What Are SQL Injection Attacks?

SQL injection technique exploits how the web pages of the target website communicate with its back-end databases. In a worst case, the hacker inserts some SQL statements into the web application via the web server and obtains the answers to those queries or achieve the execution of other related SQL statements. In case web application trusts the input entered by the user and doesn’t validate the details at the server, it is possible to be exploited by SQL injection attacks. When it comes to the data breaches situation, the SQL injection includes three main uses:

1. Query-sensitive data from databases
2. Alter significant data within databases
3. Provide malware to the application or system

Why SQL Injections Matter?

Still, the SQL language remains as the dominant way of inserting, retrieving and filtering data in the database. Even a loading of single web page requires loads of SQL queries to execute regardless of the size of the website or business. Hence, just armed with a web browser, an internet connection and some core knowledge of the SQL, cybercriminals can exploit the weakness in the web application by extracting data, determining or resetting user or admin credentials and utilizing it as an entry point for severing assaults on the network. Based on a report by Verizon Business, nearly 24% of payment card breaches happen due to SQL injection attack. This attack occupies the second position next to malware in terms of card breaches. 

Keep in mind that, this attack can function in any kind of SQL database; however, PHP-based websites are the major targets since they can be formed by anyone (for example, WordPress) and frequently includes plenty of valuable details about the clients within their database. 

Types Of SQL Injection Attack

SQL injection attacks can be categorized in various ways, according to the response received from the server, the sort of data withdrawal channel, impact point, injection point location, the intent of the attack, etc. 

Response received from the server:

  • Blind SQL Injections
  • Boolean-based blind injections.
  • Time-based blind injections.

Error-based SQL injections:

  • Union query type
  • Double query Injections

Sort of data withdrawal channel:

  • Inline
  • Out-of-band

Impact point:

  • First-order injections
  • Second-order injections

Injection point location:

  • Injection through user input form fields
  • Injection through cookies
  • Injection through server variables

Intent of attacking:

  • Identifying injectable parameters
  • Determining database schema
  • Performing database fingerprinting

Extracting data:

  • Adding or modifying data
  • Executing remote commands
  • Bypassing authentication
  • Performing privilege escalation
  • Evading detection
  • Performing denial of service

Damages Caused By SQL Injections

  • Stealing of user credentials like a username and password for criminals or commercial purpose and completely rubbing out of details or ruining the pages of the website.
  • Corruption of complete database as well as deleting of entire backups
  • Silent spying as well as monitoring activities by competitors.

SQL Injection Example

Generally, when a user of the website enters data into a front-end form on a website, then a SQL query is generated and sent to the database. For example, consider a logon form that submits the username and password submitted by the user to the database via a SQL statement. If the inputs are valid, the database responds and display the details required, whereas the inputs are not valid, the database shows an error message.

SQL Query Processing:

The below HTML code asks login information from the user:

Sql Processing
When the user clicks the login button after entering the logon information, the browser submits the following string to the server that includes the logon credentials:

sql processing 2

Let us consider, the SQL statement at the backend for validating username and password:

sql processing 3

If the user enters the information as shown below:

  • Username: admin
  • Password: E5gh@

The statement to be executed would be
sql processing with password

Let us see how the SQL injection activity happens. The diagram shows the steps that attackers were taken to exploit the authentication flaws related to username:


after sql processing

The Login Form:

the login form


Generated SQL statements and background process:

Generated SQL Statements And Background ProcessThe input bypasses the username condition by placing a single quote, making username field as blank. Now, second condition can be replaced as OR one equal to ONE, which is logically always true. We can see, two conditions are placed, and OR operator tells that at least one should be true. 
Further, it bypassed other originally placed SQL conditions, by placing two dashes and a space, telling the interpreter that remaining data is a statement, and needs to be ignored. Additional One after space is just to avoid any confusion with respect to spaces.
Here, we can see all logical conditions and requirements are completed, and original AND condition, along with password requirement is bypassed.
As a result of this execution, the attacker logged into the admin page:

width: auto; height: auto

Preventive Steps Against SQL Injection Attacks

Organizations can focus on following steps to prevent them from SQL Injection Attacks:

Never trust the user inputs – It must always be validated before use in SQL statements.

Stored procedures – These can abstract the SQL statements & consider the entire input as just parameters.

Prepared statements – It involves creating the SQL query as a first action and then treating entire submitted data as parameters. It has no influence on the SQL statement syntax.

Regular expressions – It is used to detect the harmful code and eliminate it before the SQL statement executions.

Proper error Message – This policy states that avoid revealing sensitive details and the location where the error happened on the error message.

Limited user access rights for database connection – Only required access permissions should be provided in the accounts for making a database connection. This can support minimize the SQL statements that execute dynamically on the server.

In SQL injection, hackers can trick interpreter by pushing some logical sequences of characters, along with standard commands, or keywords as per parsing engine. Hope the above details on the SQL injection attacks provided you a clear understanding on how it’s working and how to prevent it from happening.

    All Comments (0)

    No one has commented yet.

Leave a comment