Xombe trojan downloader was sent to a large amount of people in the e-mail that looks like that:
Windows XP Service Pack 1 (Express) - Critical Update.
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.
(c) 2004 Microsoft Corporation. All rights reserved. Terms of
Use Privacy Statement
When the trojan downloader is run by a user, it connects to
Internet and downloads another trojan.
The trojan consists of three components:
This file is the first-stage downloader that comes in email. The only purpose of this program is to fetch the main component of the trojan and plant in on the target system.
This is the main component of the trojan. It is a general-purpose downloader application that is controlled through a certain web page. It can fetch arbitrary files from the Internet and install them on the infected system.
msvchost.exe is installed to the System Directory on the infected
computer and added to the registry as
When the trojan was first intercepted the website instructed the clients to download a DLL file.
http_f.dll is an HTTP client which is apparently used to perform a Distibuted Denial-of-Service attack on a website that hosts forums.
This file is also dropped to the System Directory, just like the main component.