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"Failure to Preserve SQL Query Structure (aka 'SQL Injection')" appears at number 2 in the CWE/SANS TOP 25 Most Dangerous Programming Errors list published on February 16. And for good reason: SQL injection attacks pose a massive potential threat to your organization. That's because, if successful, they could allow hackers to compromise your network, access and destroy your data, and take control of your machines.
What Is SQL Injection?
The principal behind SQL injection is pretty simple. When an application takes user data as an input, there is an opportunity for a malicious user to enter carefully crafted data that causes the input to be interpreted as part of a SQL query instead of data.
For example, imagine this line of code:
SELECT * FROM Users WHERE Username='$username' AND Password='$password'
which is designed to show all records from the table "Users" for a username and password supplied by a user. Using a Web interface, when prompted for his username and password, a malicious user might enter:
1' or '1' = '1
1' or '1' = '1
resulting in the query:
SELECT * FROM Users WHERE Username='1' OR '1' = '1' AND Password='1' OR '1' = '1'
The hacker has effectively injected a whole OR condition into the authentication process. Worse, the condition '1' = '1' is always true, so this SQL query will always result in the authentication process being bypassed.
<Code sample sourced from OWASP http://www.owasp.org/index.php/Main_Page
Using characters like ";" to append another query on to the end of an existing one, and - - to comment out(and therefore cut off) a part of an existing query, a hacker could potentially delete entire tables, or change the data they contain. He could even issue commands to the underlying OS, thereby taking over the machine, and using it as a staging post to attack the rest of your network. In summary, the consequences of a SQL injection attack could be:
- Loss of data confidentiality
- Loss of data integrity
- Loss of data
- Compromise of the entire network