Microsoft on Friday found itself trying to clarify that it has nothing to do with the poor coding practices that have enabled a massive SQL injection attack to affect Web sites using Microsoft IIS Web Server and Microsoft SQL Server.

"The attacks are facilitated by SQL injection exploits and are not issues related to IIS 6.0, ASP, ASP.Net, or Microsoft SQL technologies," said Bill Sisk, a communications manager at Microsoft, in a blog post. "SQL injection attacks enable malicious users to execute commands in an application's database."

Sisk said that to defend against SQL injection attacks, developers should follow secure coding practices.

SQL injection attacks involve insufficiently filtered code submitted to SQL databases through user input mechanisms.

On Friday, U.S. CERT issued a warning about SQL injection attacks that have compromised a large number of legitimate Web sites. Affected Web sites contain injected JavaScript that attempts to exploit several known vulnerabilities. U.S. CERT recommends disabling JavaScript and ActiveX.

Because otherwise legitimate Web sites deliver this attack, SAN Internet Storm Center handler Donald Smith observes that the concept of a "trusted" or "legitimate" site is no longer meaningful. The attack has reportedly affected the Web sites of the United Nations and the U.S. Department of Homeland Security, to name a few.

On Thursday, computer security firm F-Secure said that it had found the offending JavaScript code on over half a million Web pages. The company said that IT administrators should immediately block nmidahena.com, aspder.com, and nihaorr1.com, three domains associated with the injection attack.

Google may have taken some action to remove some of the affected pages from its index. A Google search for a text string associated with the malicious JavaScipt now yields only 56,700 results. A screenshot of what is presumably a similar Google search -- the exact string is blurred -- performed by F-Secure last week shows 510,000 results.

A search using the same text string on Microsoft's Live Search returns 268,000 results. Yahoo Search returns 560,000 results for the text string in question.

Patrick Runald, a security researcher at F-Secure, explained in a blog post that the attack "finds all text fields in the database and adds a link to malicious JavaScript to each and every one of them which will make your Web site display them automatically. So essentially what happened was that the attackers looked for ASP or ASPX pages containing any type of querystring (a dynamic value such as an article ID, product ID, et cetera) parameter and tried to use that to upload their SQL injection code."

Runald reiterated Sisk's point that poorly written ASP and ASPX (.net) was to blame rather than any specific vulnerability in Microsoft's software.