SQL Injection is a technique used to exploit web sites by altering backend SQL statements through manipulating application input. SQL Injection happens when a developer accepts user input that is directly placed into a SQL Statement and doesn't properly filter out dangerous characters. This can allow an attacker to not only steal data from your database, but also modify and delete it. Certain SQL Servers such as Microsoft SQL Server contain Stored and Extended Procedures (database server functions). If an attacker can obtain access to these procedures it may be possible to compromise the entire machine. Attackers commonly insert single quotes into a URL's query string, or into a forms input field to test for SQL Injection.