By now, you've probably heard that someone leaked a significant portion of the Microsoft Windows source code to the Internet during the early months of 2004. How this will ultimately affect the security and stability of both the Windows platform and the Internet is yet to be determined.

Microsoft operating systems and applications are already the primary targets for malicious code. Now that some of the Windows source code is "in the wild," I think it's simply a matter of time before we see exploitations of visible flaws found in the Windows source code.

It's considerably more difficult to find exploits in compiled code, yet people do so all the time. Having access to the source code makes the process that much easier.

Thus, Microsoft has found itself in the unfortunate position of getting a peer review by hackers, so it makes sense that antivirus companies will try to determine where the exploits are before they occur. I'll bet that all of the major antivirus companies are—in one way or another—looking at the leaked Windows code.
This is one more reason why it's an absolute necessity to install antivirus software on any PC using Windows—even if a firewall already protects it. And it highlights the need to keep both Windows operating systems and antivirus software updated—on a daily basis, if possible.

However, many users are surprised to learn that the majority of preinstalled antivirus software on PCs eventually ceases to update. After a period of time--sometimes only 30 days, sometimes longer--the computer system loses this protection from malicious code.

Rather than continue to harp on the central cause of insecurity, which is the lack of understanding and proper operation of computers, I'll simply suggest that people use free antivirus software, such as Grisoft's AVG Free Edition which is free for personal use.

In addition, if your preinstalled antivirus software is no longer updating, check out Trend Micro's free  Housecall service. It runs from a Web browser, and it's a quick way to check for problems before installing anything.

Also, you can check your PC for any spyware by installing and running Lavasoft's free Ad-Aware software.