Email-Worm:W32/Bagle.C

Classification

Category:

Malware

Platform:

W32

Type:

Email-worm

Aliases:

Email-Worm.Win32.Bagle.c

Summary

This type of worm is embedded in an email attachment, and spreads using the infected computer's emailing networks.

Removal

Technical Details

Email-Worm:W32/Bagle.C distributes copies of itself as file attachments to email messages that use differing subject lines. Once executed, the worm functions as a backdoor and disables certain security software.

Bagle.C was first found in the wild in the early morning of February 28th, 2004. This variant was programmed to stop spreading after March 14th, 2004.

Infection

Email-Worm:W32/Bagle.C arrives as a zipped EXE file attachment to email messages that use differing subject lines. The attachment uses the icon of a Microsoft Excel spreadsheet file as a decoy:

On initial execution, the worm starts the Windows Notepad (notepad.exe) to conceal its activity. It then drops several files to the Windows System Directory:

%SysDir%\readme.exe - dropper of other components
%SysDir%\onde.exe - main worm body
%SysDir%\doc.exe - external library helper

'Readme.exe' is added to the registry as

[HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\gouday.exe]

to ensure that the worm will be activated when Windows starts. To indicate whether the worm was run for the first time it creates another value in the registry as

[HKCU\Software\DateTime2\frun]

Activity

Bagle.C comes with a backdoor that listens on a TCP port 2745, which is hardcoded in the worm's body. The backdoor provides full remote access to the infected computer. It can be used to download and execute arbitrary programs from the Internet. When the worm is started it connects to a list of predefined web servers and tries to access a PHP file with certain parameters. One of the parameters is the TCP port where the backdoor is listening which suggests that this functionality is used to collect the addresses of infected computers. The payload of Bagle.C contains a thread that terminates processes with the following names:

ATUPDATER.EXE
AVWUPD32.EXE
AVPUPD.EXE
LUALL.EXE
DRWEBUPW.EXE
ICSSUPPNT.EXE
ICSUPP95.EXE
UPDATE.EXE
NUPGRADE.EXE
ATUPDATER.EXE
AUPDATE.EXE
AUTODOWN.EXE
AUTOTRACE.EXE
AUTOUPDATE.EXE
AVXQUAR.EXE
CFIAUDIT.EXE
MCUPDATE.EXE
NUPGRADE.EXE
OUTPOST.EXE
AVLTMAIN.EXE

Propagation (email)

Bagle.C recursively searches all drives on the infected computer to locate file that could contain email addresses. It parses these files and collects all email addresses it can find. Files with the following extensions are checked:

.wab
.txt
.htm
.html
.dbx
.mdx
.eml
.nch
.mmf
.ods
.cfg
.asp
.php
.pl
.adb
.sht

The mailer routine will ignore all the addresses that contain the any of these strings:

.ch
@hotmail.com
@msn.com
@microsoft
@avp.
noreply
local
root@
postmaster@

Using its own SMTP engine Bagle sends messages with infected attachments to the collected addresses. The SMTP engine uses direct Mail eXchange (MX) lookup on the target domain so it does not depend on email settings of the infected computer. The body of the messages is empty. The sender address in the email is spoofed. The infected emails can have the following subjects: