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SQL injection: Secure your Web applications

SQL injection exploits wreak havoc on vulnerable Web sites. Expert Caleb Sima explains how to protect your applications against these popular and destructive injection attacks.

SQL injection exploits may soon be as common as those targeting Windows and Unix flaws, experts say. An estimated 60% of Web applications that use dynamic content are likely vulnerable, with devastating consequences for an enterprise. Learn how to recognize whether your sites are vulnerable.

Step 1. Open the Web site in a browser.

Step 2. Mouse over the links of the Web site with your cursor while paying attention to the bottom status bar. You will notice the URLs that the links point to. Try to find a URL with parameters in it. Ex. http://www.site.com/articleid.asp?id=42. Most SQL injection problems are present when the file extensions are ".asp" or ".cfm". When trying to test a site for SQL injection vulnerabilities, look for these files specifically.

Note: If you don't see any URL's in the status bar, then just click on links and watch the address bar until you find a URL that has parameters.

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Step 3. Once a URL with parameters has been found, click the link and go to that page. In the Address bar you should now see the URL that was seen in the status bar.

Step 4. Here is where the actual testing takes place. There are two methods for testing script for SQL injection. Be sure to test each parameter value one at a time with both methods.

Method 1. Go to the address bar, click your cursor, and highlight a parameter value Ex. Highlight the word value in "name=value" and replace it with a single quote (').It should now look like "name='"

Method 2. Go to the address bar, click your cursor, and put a single quote (') in the middle of the value. It should now look like "name=val'ue"

Step 5. Click the 'GO' button. This will send your request to the Web server.

Step 6. Analyze the response from the Web server for any error messages. Most database error messages will look similar to the examples below:

Example error 1:
Microsoft OLE DB Provider for SQL Server error '80040e14'
Unclosed quotation mark before the character string '51 ORDER BY
some_name'. /some_directory/some_file.asp, line 5

Example error 2:
ODBC Error Code = S1000 (General error)
[Oracle][ODBC][Ora]ORA-00933: SQL command not properly ended

Step 7. Sometimes the error message is not obvious and is hidden in the source of the page. To look for it, you must view the HTML source of the page and search for the error. To do this in Internet Explorer, click the 'View' menu, and select the 'Source' option. This will cause notepad to open with the HTML source of the page. In notepad, click the 'Edit' menu and select 'Find'. A dialog box will appear that will ask you to 'Find What'. Type the phrase 'Microsoft OLE DB' or '[ODBC]' and click 'Find Next'.

Step 8. If either step 6 or 7 is successful, then the Web site is vulnerable to SQL injection.

This tip originally appeared on SearchSecurity.com.

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