Understanding SQL Injection Attacks

Understanding SQL Injection Attacks is very paramount to building a secure web application.

SQL injection is an attack in which SQL code is inserted or appended into application/user input parameters that are later passed to a back-end SQL server for parsing and execution.

The primary form of SQL injection consists of direct insertion of the code into parameters that are concatenated with SQL commands and executed.

When an attacker is able to modify an SQL statement, the process will run with the same permissions as the component that executed the command (e.g. database server, application server, or Web server), which is often highly privileged.

There are lots of ways to encode the quote character so that it is accepted as input, and some SQL injection vulnerabilities can be exploited without using it at all. Also, the quote character is not the only character that can be used to exploit SQL injection vulnerabilities; a number of characters are available to an attacker, such as the double pipe (||) and double quote (“), among others.

Understanding How SQL Inject Attacks Work

SQL injection vulnerabilities most commonly occur when the Web application developer does not ensure that values received from a Web form, cookie, input parameter, and so forth are validated or encoded before passing them to SQL queries that will be executed on a database server.

If an attacker can control the input that is sent to an SQL query and manipulate that input so that the data is interpreted as code instead of as data, he may be able to execute code on the back-end database.

Without a sound understanding of the underlying database that they are interacting with or a thorough understanding and awareness of the potential security issues of the code that is being developed, software application developers can often produce inherently insecure applications that are vulnerable to SQL injection.

How to Prevent SQL Injection

Programming languages that do not validate input before passing it to a dynamically created SQL statement are potentially vulnerable; that is, unless it uses parameterized queries and bind variables.

Understanding how SQL injection attacks work therefore becomes something of necessity to a security-conscious software developer.