A new Trojan downloader posing as a Windows Service Pack update program is being spammed, says Trend Micro here.
Listed as having high damage potential, TROJ_XOMBE.A comes as a 'Critical Update' with WINXP_SP1.EXE as an attachment.
The message reads:
"Window Update has determined that you are running a beta version of Windows XP Service Pack 1 (SP1). To help improve the stability of your computer, Microsoft recommends that you remove the beta version of Windows XP SP1 and re-install Windows XP SP1. If you cannot remove the beta version, you should still reinstall Windows XP SP1.
"Windows XP SP1 provides the latest security, reliability, and performance updates to the Windows XP family of operating systems. Windows XP SP1 is designed to ensure Windows XP platform compatibility with newly released software and hardware, and includes updates to resolve issues discovered by customers or by Microsoft's internal testing team.
"The maximum download size is approximately 3 MB, however the size of the download and time required may be less for computers that have had updates previously installed.
"To minimize the download time needed for installation, setup will only download those files which are required to bring your computer up to date. Windows XP SP1 includes Internet Explorer 6 SP1. Anti-virus software programs may interfere with the installation of Windows XP SP1. Please disable anti-virus software while installing the service pack.
"Just run the file winxp_sp1.exe in attach and make sure to restart your PC after installation will be completed.
The attachment downloads and executes the file MSVCHOST.EXE, which is detected as BKDR_XOMBE.A and runs on Windows 95, 98, ME, NT, 2000 and XP, says Trend.