Example of SQL Injection
Take a simple login page where a legitimate user would enter his username and password combination to enter a secure area to view his personal details or upload his comments in a forum.
When the legitimate user submits his details, an SQL query is generated from these details and submitted to the database for verification. If valid, the user is allowed access. In other words, the web application that controls the login page will communicate with the database through a series of planned commands so as to verify the username and password combination. On verification, the legitimate user is granted appropriate access.
Through SQL Injection, the hacker may input specifically crafted SQL commands with the intent of bypassing the login form barrier and seeing what lies behind it. This is only possible if the inputs are not properly sanitised (i.e., made invulnerable) and sent directly with the SQL query to the database. SQL Injection vulnerabilities provide the means for a hacker to communicate directly to the database.
The technologies vulnerable to this attack are dynamic script languages including ASP, ASP.NET, PHP, JSP, and CGI. All an attacker needs to perform an SQL Injection hacking attack is a web browser, knowledge of SQL queries and creative guess work to important table and field names.