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What is a SQL Injection Attack?

Published: March 4, 2011

SQL injection attacks are real threats to websites because they attack the heart of a website which is the database.  The database is vital in that it stores not only the data but also all the applications that websites need to function.  The database is where we store sensitive user information, preferences, inventory, invoices, payments etc .


SQL stands for Structured Query Language, comes in various dialects and is mostly based on the SQL-92 ANSI standard.  SQL queries are made up of one or more SQL commands.  Examples of these commands are SELECT, UPDATE or INSERT.  In regards to SELECT queries, there is often a clause that instructs data to be returned to a specific area within the database.  These queries not only make the SQL language very popular but it is also what makes it very vulnerable to these SQL Injection Attacks.  How an SQL injection attack works is by "injecting" - adding SQL code to a query which allows a database to be manipulated in ways which were not intended.


You can avoid these SQL attacks by making sure that you design your scripts and your applications with the utmost care.  Following is a few ways in which you can reduce the vulnerability of your website to these attacks:


  1. Limit User Access - Never use the default system account for the SQL server 2000 as it has an unrestricted nature.  Always set up specific accounts for specific purposes.  An example of this would be in the circumstance of letting users view and order products.  Set up a specific account for the user where they SELECT only on the products table and can INSERT only on the orders table.
  2. One of the more damaging SQL injection attacks target several extended stored procedures.  If you don't use them, then remove extended stored procedures, unused triggers, stored procedures, user-defined functions etc.  By removing these vulnerabilities, you are actually blocking the attack before it can happen.
  3. Escape Quotes - Most of SQL Injection Attacks look for the user of single quotes to terminate an expression.  To really reduce the opportunity for an attack, simply replace all single quotes to two single quotes by using a replace function.  By doing this, the clause for the WHERE query now requires both the username and the userpass fields in order to be valid.
    3) Remove Culprit characters or character sequences - We have found that certain characters and character sequences are often used to perform a SQL injection attack.   Before you build a query, get rid of these characters and character sequences to reduce your injection attack vulnerability.
  4. Limit the length of user input - Keep all form fields and text boxes as short as possible.  By doing this you are limiting the number of characters that can be used to create a SQL injection attack.

It is not always possible to prevent SQL Injection Attacks but you are now armed with a few ways to guard against them.


About the Author
Anna Agnew is an author for The Computer Geek Custom Web Page Design. The Computer Geek is a web design company that prides itself in professional service at a fraction of the cost. The Computer Geek specializes in Custom Web Design, PHP & MySql and Ecommerce.



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