A new polymorphic virus - worm known as Bugbear.B was found in the
wild in the early morning on June 5th, 2003. The worm sends e-mails
with various contents. It uses a known vulnerability to execute the
attachment automatically when the e-mail is opened.
UPDATE (2003-06-05 15:00 GMT)
F-Secure is raising the alert level on Bugbear.B (Tanatos.B) to level 1
as it continues to spread rapidly. The number of reported infections
have increased drastically over the last 10 hours.
Disinfection
F-Secure provides a special tool to disinfect the Bugbear.B worm.
The tool and disinfection instructions are available on our ftp
site:
The worm's file is a Windows PE executable file compressed with
UPX file compressor and encrypted with a simple cryptoalgorithm
that changes in every worm generation making the worm
polymorphic. The packed worm's file size is 72192 bytes, the
unpacked size is over 170 kilobytes.
System infection
When the worm's file is run, it installs itself to system by
infecting files of several popular applications and system tools.
The following files in Program Files and Windows folders are
infected:
where %ProgramFilesDir% is a Program Files directory and %WinDir%
is Windows directory.
The worm can also drop its file to Startup folder with a random
name or as SETUP.EXE, so it will be activated on next system
restart. Additionally the worm drops a keylogging component in
Windows System directory with a random name and DLL extension.
The name can be MGLKCKK.DLL for example. Also the worm creates 2
additional files in Windows System folder where it stores its
data in encrypted form.
Spreading in e-mails
The worm spreads in e-mail messages. It has its own SMTP engine.
To find e-mail addresses the worm looks for files with the
following names and extensions:
.ODS
.MMF
.NCH
.MBX
.EML
.TBB
.DBX
INBOX
Some of such files are e-mail databases and they contain a lot of
e-mail addresses. The worm sends itself to all found addresses.
However, it avoids sending itself to e-mail addresses containing
any of the following:
The subject of an infected message is either taken from random
files on an infected computer or selected from the following
list:
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Introduction
various
Announcement
history screen
Correction of errors
Just a reminder
Payment notices
hmm..
update
Hello!
The body of an infected message can be empty or it can contain a
text from a random file on an infected computer. In some cases
the worm can send out confidential data, for example parts of
private e-mail messages and document files.
The body of an infected message can contain I-Frame exploit. It
allows the worm to run automatically on some computers when an
infected e-mail is viewed (for example, with Outlook and IE 5.0
or 5.01). This vulnerability is fixed and a patch for it is
available on Microsoft site:
The attachment name can be SETUP.EXE or it can contain one of the
following strings:
readme
Setup
Card
Docs
news
image
images
pics
resume
photo
video
music
song
data
The worm can also "borrow" a name from a random file on an
infected computer. The extension of an infected attachment is
selected from the following list:
exe
scr
pif
In case the worm used a file's name from an infected computer,
the worm's attachment can have 2 or more extensions, for example
DOCUMENT.DOC.EXE . The worm checks the extension of the file it
borrows the name from and sets the content type of its attachment
in an infected message accordingly.
Extensions the worm checks:
reg
ini
bat
h
diz
txt
cpp
c
html
htm
jpeg
jpg
gif
cpl
dll
vxd
sys
com
exe
bmp
The worm fakes sender's e-mail address, so if you receive an
infected message please do not reply to it as it will most likely
go to a person whose computer is not infected by the worm.
Please note that Bugbear.B worm can send out corrupted attachments
that will not run. Such attachments are usually shorter than the
original worm's file.
Spreading in local network
The worm has the ability to infect remote computers over a local
network. It waits for some time before starting its infection
cycle and then enumerates network shares, connects to them and
tries to infect the following files in Program Files and Windows
folders on remote computers:
where %ProgramFilesDir% is a Program Files directory and %WinDir%
is Windows directory.
Also the worm tries to locate common startup folder on remote
computers and copies itself there as SETUP.EXE or with a random
name and .EXE extension.
As a result remote computers will become infected either after
restart or after a user there runs an infected file.
Killing processes
The worm kills processes of certain anti-virus, security and
other programs. It lists active processes every 20 seconds and
terminates processes whose file names match any of the following:
The worm has separate process killing routines for Windows 9x and
Windows NT-based operating systems.
Backdoor component
The worm has a backdoor component similar to the one used in its
previous version. The backdoor listens to TCP port 1080 for
commands from a remote host. A hacker can connect to the backdoor
and perform the following action:
- get information about infected computer
- upload and download files
- start files
- delete files
- terminate processes
- get process list
- start keylogger
- start HTTP server on a selected port
Here's how the interface of Bugbear's HTTP server looks like:
The Bugbear.B worm's backdoor does not use secure authentication
like its previous variant, so the backdoor can be used by many
hackers, not just the worm's author.
Keylogging component
The keylogging DLL dropped by the worm, saves user's keystrokes
into a file with a random name and DLL extension located in
Windows System folder. The worm periodically sends this file to a
randomly selected e-mail address from the list of addresses
stored together with the corresponding SMTP server names inside
the worm's body. The e-mail addresses and SMTP server names are
stored in encrypted form.
Affecting bank computers
The worm has a large list of domains belonging mostly to banks.
At startup the worm checks the domain name of an infected
computer and then compares it to the its internal list. If the
domain name matches, the worm enumerates cached passwords and
sends them to a randomly selected e-mail address from the list of
addresses stored together with the corresponding SMTP server
names inside the worm's body. The e-mail addresses and SMTP
server names are stored in encrypted form. This list is different
from the one that the worm sends the keylogger-generated file to.
The worm temporarily disables AutoDial feature on an infected
computer by modifying the following Registry key:
After sending the files, the worm restores the key to its
original value. The actions described above, make banks'
computers more vulnerable than other infected computers as stolen
passwords might be used by a hacker to access infected banks'
networks from remote computers.
The list of bank domains that the worm has includes banks from
many different countries: France, UK, Germany, Australia, Italy,
Greece, Denmark, New Zealand, Spain, Brasil, Romania, Poland,
Argentina, Switzerland, Finland, Taiwan, Turkey, Iceland,
Slovakia, Korea, USA, South Africa, Baltic Republics, Austria,
Hungary, Norway, Czech Republic and some other countries.
Side Effect
According to reports, network printers start to print a lot of
garbage when the worm spreads in a network. This might be the
side-effect of the worm's attempts to infect a network.
