W32/Swen@MM

-- Update October 9th 02:00 PST --
Two additional variants of this worm have been received by AVERT, created by minor edits of certain strings within the initial worm, and subsequent packing with UPX. Both are already detected as virus or variant W32/Swen@MM with the 4294 DATs or greater.

Exact identification of the first (as W32/Swen@MM ) was included in the 4297 DATs. Exact identification of the latter will be included in 4298 DATs.

Both of these variants are of filesize 52,224 bytes.

-- Update September 19th 13:00 PST --
AVERT has released a standalone removal tool to aid users in removing this virus from infected systems.  If you're unable to run .exe files, you may need to install this fixswen.inf  first (save the fixswen.inf file to your local hard disk, right-click on the file and choose install ).

-- Update September 18th 09:27 PST --
Due to an increase in prevalence of this worm, AVERT is raising the risk assessment to MEDIUM for Home Users.

Sometimes purporting to be a Microsoft Security Update, this worm is intended to propagate via various mechanisms:

• mailing itself to recipients extracted from the victim machine
• copying itself over network shares (mapped drives)
• sharing itself over the KaZaa P2P network
• sending itself via IRC

The worm is written in MSVC. Though in a different HLL, it bears similarities to W32/Gibe.b@MM   (original Gibe variants were written in VB).

The worm terminates processes relevant to various security and anti-virus products (see below).

Proactive Detection : This worm is detected as "virus or variant New Worm" with the 4120 DATs or greater (with program heuristics enabled).

Mail Propagation

The virus contains its own SMTP engine to construct outgoing messages.

Various outgoing messages are created. Some make use of an IE exploit  to ensure the worm attachment is run upon viewing the email. See Microsoft Security Bulletin (MS01-020) . One such message bears the following characteristics:

Subject : Returned Response
From : Email Delivery Service (kmailengine@yahoo.com)
Body : Undeliverable mail to (email address )

Messages constructed to take advantage of this vulnerability will be detected as Exploit-MIME.gen.exe with the 4215 DATs or greater (and earlier as Exploit-MIME.gen).

Multiple subject lines and attachment names are constructed from pools of strings within the worm to be used in outgoing messages. Target, Source and Reply email addresses are extracted from files on the victim machine.  The collected addresses are used to construct both sender and recipient addresses.

At least one message masquerades as a Microsoft update:

Share Propagation

The worm copies itself to the startup folder on mapped network drives. A random filename is used.

The following network locations are targetted:

• windows\all users\start menu\programs\startup
• windows\start menu\programs\startup
• winme\all users\start menu\programs\startup
• winme\start menu\programs\startup
• win95\all users\start menu\programs\startup
• win95\start menu\programs\startup
• win98\all users\start menu\programs\startup
• win98\start menu\programs\startup
• document and settings\all users\start menu\programs\startup
• document and settings\default user\start menu\programs\startup
• document and settings\administrator\start menu\programs\startup
• winnt\profiles\all users\start menu\programs\startup
• winnt\profiles\default user\start menu\programs\startup
• winnt\profiles\administrator\start menu\programs\startup

IRC Propagation

The worm drops a SCRIPT.INI file (123 bytes) into the mIRC program folder in an attempt to propagate via IRC (using dcc send). This file is proactively detected as MIRC/Generic with the 4149 DATs or greater.

P2P Propagation

The worm makes copies of itself in a directory (random name) within the system temp directory. Enticing filenames are used, for example:

• SIRCAM CLEANER.EXE
• YAHOO HACKER.EXE
• HALLUCINOGENIC SCREENSAVER.EXE
• etc etc

The following Registry key is modified to share these copies via the KaZaa P2P network:

HKEY_CURRENT_USER\Software\Kazaa\LocalContent
"Dir99" = 012345:C:\WINDOWS\TEMP\(random directory name)

Propagation via Newsgroups

The worm carries a compressed list of newsgroup servers.  At run time, the list is decompressed and written to a temp file.  The worm uses the default newsgroup server from the machine or one from the list to post messages to a randomly selected group.  The message is the same from the email propagation.

• Display of the above dialog boxes
• Unexpected termination of AV/security product
• Inability to run RegEdit on the victim machine

Installation

When run on the victim machine, a sequence of fake message boxes are displayed:

The worm installs itself (using a random filename) into %WinDir%, for example:

C:\WINDOWS\ZNFUL.EXE

A Registry key is added to hook system startup, for example (random string and filename will obviously change):

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Run "(random string)" = ZNFUL.EXE autorun

Various Registry keys are modified to hook the execution of the following file types:

• BAT
• COM
• EXE
• PIF
• REG
• SCR

For this, the following Registry keys are set:

HKEY_CLASSES_ROOT\batfile\shell\open\command
"(Default)" = %filename% "%1" %*

HKEY_CLASSES_ROOT\comfile\shell\open\command
"(Default)" = %filename% "%1" %*

HKEY_CLASSES_ROOT\exefile\shell\open\command
"(Default)" = %filename% "%1" %*

HKEY_CLASSES_ROOT\piffile\shell\open\command
"(Default)" = %filename% "%1" %*

HKEY_CLASSES_ROOT\regfile\shell\open\command
"(Default)" = %filename% showerror

HKEY_CLASSES_ROOT\scrfile\shell\config\command
"(Default)" = %filename% "%1"

HKEY_CLASSES_ROOT\scrfile\shell\open\command
"(Default)" = %filename% "%1" /S

(Where %filename% is the random filename which the worms installs into %WinDir% as.)

The following files are also dropped:

• %WinDir%\GERMS0.DBV   - email addresses harvested from the victim machine are written to this file (: delimitted)
• %WinDir%\SWEN1.DAT   - list of remote servers

Other randomly named files may also be dropped in %WinDir% - a batch script (approx 50 bytes) for launching the dropped copy of the worm, and a config file (approx 100-150 bytes) containing path/filename data.

The following Registry key is set in order to prevent RegEdit being used on the victim machine:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
Policies\System "DisableRegistryTools" = 01 00 00 00

Other data is written to the Registry stored under the following key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\explorer\%random string%

Where %random string% is a random text string.

The following values are stored here:

• "Install Item" = (random string used for installed copy of worm in %WinDir%)
• "Installed" = ... by Begbie
• "Kazaa Infect" = yes
• "Mirc Install Folder" = C:\Program Files\mirc
• "Unfile" = buzf.qtq
• "ZipName" = wqrqgd

The worm also displays a fake dialog window concerning a MAPI32 Exception. The user is prompted to submit:

• email From name
• login name/password
• email address
• SMTP server
• POP3 server

Process Termination

The worm terminates various processes on the victim machine (see below). Interesting, the list includes "gibe"!

• _avp
• ackwin32
• amserv
• anti-troj
• aplica32
• apvxdwin
• autodown
• avconsol
• ave32
• avgcc32
• avgctrl
• avgw
• avkserv
• avnt
• avp
• avsched32
• avwin95
• avwupd32
• blackd
• blackice
• bootwarn
• ccapp
• ccshtdwn
• cfiadmi
• cfiaudit
• cfind
• cfinet
• claw95
• dv95
• ecengine
• efinet32
• esafe
• espwatch
• f-agnt95
• f-prot
• f-prot95
• f-stopw
• findviru
• fp-win
• fprot
• fprot95
• frw
• gibe
• iamapp
• ibmasn
• ibmavsp
• icload95
• icloadnt
• icmon
• icmoon
• icssuppnt
• icsupp
• iface
• iomon98
• jedi
• kpfw32
• lockdown2000
• lookout
• lu32
• luall
• moolive
• mpftray
• msconfig
• nai_vs_stat
• nav
• navapw32
• navnt
• navsched
• navw
• nisum
• nmain
• normist
• nupdate
• nupgrade
• nvc95
• outpost
• padmin
• pavcl
• pavsched
• pavw
• pcciomon
• pccmain
• pccwin98
• pcfwallicon
• persfw
• pop3trap
• rav
• regedit
• rescue
• safeweb
• serv95
• sphinx
• sweep
• tca
• tds2
• vcleaner
• vcontrol
• vet32
• vet95
• vet98
• vettray
• view
• vscan
• vsecomr
• vshwin32
• vsstat
• webtrap
• wfindv32
• zapro
• zonealarm

If one of these processes is started when the worm is running, a fake error message is displayed "Memory access violation in module kernel32 at (number)".

Infection Counter

Once running on the victim machine, the worm issues a HTTP request for a remote page which serves as an infection counter.

-- Update September 19th --

The original animated counter has been replaced by a warning message indicating the potential infection. In the text, the virus is referred to as W32/Swan@MM:

DAT Files
Detection is included in the 4294 DAT files . In addition to the DAT version requirements for detection, the specified engine version (or greater) must also be used.

Stand Alone Remover
Stinger has been updated to include detection/removal of this threat.

As stated above W32/Swen@MM disables the execution of REGEDIT.EXE.  

This fixswen.inf tool will reverse the changes made by the virus and allow the user to execute REGEDIT.EXE as normal.  In addition, it will also allow BAT, COM, EXE, PIF, REG and SCR files to run, if the virus was deleted without correcting the registry changes.  Save the fixswen.inf file to your local hard disk, right-click on the file and choose install.

NOTE: When using McAfee products, users should always choose the CLEAN option, over the DELETE option as simply deleting a virus will not clean any necessary registry entries.

The changes made to the Registry to hook BAT, COM, EXE, PIF and  SCR file execution (as detailed above) will be removed when cleaning with the specified Engine and DATs.

Additional Windows ME/XP removal considerations

W32/Swen.dam