Microsoft's patch process has spawned an attempt to fool Windows users into downloading and installing a Trojan horse.

A fake e-mail message, sent to CNET News.com, purports to be a Microsoft security notification about problems with the Windows operating system. The message, which carries the subject line "MS Windows/Critical Error," attempts to fool PC users into downloading and installing an attached program. However, numerous spelling and grammar errors in the message could tip people off to the danger. "In the libraries of OS Windows(r) critical errors have been found," reads the e-mail message that contains the Trojan horse attachment. "This errors lead to destruction of the system files from your computer without an opportunity on restoration." The attached executable file, named Windowsupdate.rar, appears to be a Windows archive file, a format used to install code on PCs. Antivirus company Symantec said the file is not listed in the virus database, so it's unclear whether the file is a virus, a prank or any other kind of attack.