Sober.K

Threat description

Details

Summary

Sober.K worm was seeded in e-mails on 21st of February 2005. It is quite similar to the previous variants. Sober.K sends itself as an attachment in e-mail messages with English or German texts.

Removal

Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

The worm is written in Visual Basic. The worm's file is a UPX packed PE executable about 52 kilobytes long. The unpacked worm's file size is over 179 kilobytes. The worm adds random garbage to the end of its file every time it installs itself on a computer.

Installation to system

When the worm's file is started it opens Write text editor with the following text as a decoy:

When the worm's file is run, it copies itself with 3 different names to %WinDir%\msagent\win32\ folder:

csrss.exe
smss.exe
winlogon.exe
 

These files are identical to the worm's copy except for byte at offset 0xA0. This byte is different in every dropped copy. The worm always keeps 2 of its processes in memory.

Sober.K worm adds startup keys for one of these files in System Registry:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"_winsystem.sys" = "%WinDir%\msagent\win32\smss.exe"
[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
"winsystem.sys" = "%WinDir%\msagent\win32\smss.exe"
 

If these keys are deleted, the worm re-creates them after a few seconds.

Also the worm drops a few empty files to Windows System and to the main installation folder. These files are used to deactivate previous variants of the worm:

runnowso.ber
nonrunso.ber
stopruns.zhz
 

The worm creates a few data files in the main installation folder:

datamx1.dat
datamx2.dat
datamx3.dat
goto1.dat
goto2.dat
goto3.dat
zippedso1.ber
zippedso2.ber
zippedso3.ber
 

The 'datamx' and 'goto' files are used to store e-mail addresses collected from an infected computer's hard drive. The other 3 files are used to store the ZIPped worm's copy (it will be used for spreading).

Also the worm drops the 'read.me' file to Windows folder. This file contains the following text:

Ist eine weitere Test-Version. Lauft nur ein paar Tage!
In diesem Sinne:
Odin alias Anon
 
Spreading in E-mails

The worm sends different types of e-mail messages with English and German texts and its file attached. The attachment is a ZIP archive containing the worm's executable. Here's a screenshot of an infected message sent by the worm:

Before spreading the worm scans files with certain extensions on all hard disks to harvest e-mail addresses. Files with the following extensions are scanned:

pmr
phtm
stm
slk
inbox
imb
csv
bak
imh
xhtml
imm
imh
cms
nws
vcf
ctl
dhtm
cgi
pp
ppt
msg
jsp
oft
vbs
uin
ldb
abc
pst
cfg
mdw
mbx
mdx
mda
adp
nab
fdb
vap
dsp
ade
sln
dsw
mde
frm
bas
adr
cls
ini
ldif
log
mdb
xml
wsh
tbb
abx
abd
adb
pl
rtf
mmf
doc
ods
nch
xls
nsf
txt
wab
eml
hlp
mht
nfo
php
asp
shtml
dbx
 

The found e-mail addresses are saved into 6 files that the worm creates in its main installation folder:

datamx1.dat
datamx2.dat
datamx3.dat
goto1.dat
goto2.dat
goto3.dat
 

When the worm is active in memory it blocks access to these files as well as to its MIME-encoded files and all 3 executable files.

The worm ignores e-mail addresses that contain any of the following substrings:

ntp-
ntp@
ntp.
info@
test@
@www
@from.
support
smtp-
@smtp.
gold-certs
ftp.
.dial.
.ppp.
anyone
subscribe
announce
@gmetref
sql.
someone
nothing
you@
user@
reciver@
somebody
secure
whatever@
whoever@
anywhere
yourname
mustermann@
.kundenserver.
mailer-daemon
variabel
noreply
-dav
law2
.sul.t-
.qmail@
t-ipconnect
t-dialin
ipt.aol
time
freeav
@ca.
abuse
winrar
domain.
host.
viren
bitdefender
spybot
detection
ewido.
emsisoft
linux
google
@foo.
winzip
@example.
bellcore.
@arin
mozilla
iana@
iana-
@iana
@avp
icrosoft.
@sophos
@panda
@kaspers
free-av
antivir
virus
verizon.
@ikarus.
@nai.
@messagelab
nlpmail01.
clock
 

The worm composes e-mails with both English and German texts. If the worm sends infected messages to domains with suffixes '.de', '.ch', '.at' and also to 'gmx.' domain, it composes messages in German, otherwise English messages are composed.

The worm composes the following English messages:

Subjects:

Your new Password
Mail_delivery_failed
Paris Hilton, pure!
Alert! New Sober Worm!
You visit illegal websites
 

Senders:

service
webmaster
register
hostmaster
postmaster
police
Officer
Admin
Web
FBI
Michele@yahoo.com
Melanie@yahoo.com
security@microsoft.com
 

Body texts:

Thanks for your registration!
We have received your payment.
For more detailed information, read the attached text.
 

---- or ----

This is an automatically generated Delivery Status Notification.
ESMTP Error []
I'm afraid I wasn't able to deliver your message.
This is a permanent error; I've given up. Sorry it didn't work out.
The full mail-text and header is attached
 

---- or ----

More than 50 HOT Hilton Videos
More than 3000 Hilton picks
FREE Download until April, 2005
Make your own Download Account, it's free!
Further details are attached
Thanks & have fun ;)
 

---- or ----

ATTENTION!
Antivirus vendors are warning of a new variant of the Sober
virus discovered today that can delete the hard disk.
Protection:
Download and read the zipped patch. It's very easy to install!
Thanks for your cooperation!
--- (c)2005 Microsoft Corporation. All rights reserved
--- Microsoft Corporation
--- One Microsoft Way
--- Redmond, Washington 98052-6399
 

---- or ----

Dear Sir/Madam,
we have logged your IP-address on more than 40 illegal Websites.
Important: Please answer our questions!
The list of questions are attached.
Yours faithfully,
M. John Stellford
++-++ Federal Bureau of Investigation -FBI-
++-++ 935 Pennsylvania Avenue, NW, Room 2130
++-++ Washington, DC 20535
++-++ (202) 324-3000
 

Attachments:

text.zip  register_.zip  header_.zip  register.zip  text_.zip  help-text.zip  patch_.zip  indictment_cit.zip  text-.zip   

where <random> is a randomly generated number. The attachment name can be a combination of the above given file names as well.

The worm can add a fake anti-virus scanning report to its infected messages:

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

Followed by:

*-*  Anti-Virus Service  *-* http://www.   

where <domain> is the domain name of a recipient.

The worm composes the following German messages:

Subjects:

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

Senders:

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

Body texts:

## Diese E-Mail wurde automatisch generiert  ## Aus Gruenden der Sicherheit, bekommen Sie diese E-Mail  ## wenn Ihr aktuelles Benutzer- Passwort veraendert wurde  ---------------  Ihr neues Passwort und weiter Informationen befinden sich im beigefuegten Dokument.  **** Ein Service von  **** http://www.  **** Mail: Help-Line   

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

Attachments:

PSW-Text.zip  zipped-text.zip  zipped-mail.zip  Register-Info.zip  Formular.zip  Tool.zip  Patch-.zip   

where <random> is a randomly generated number.

The worm can add a fake anti-virus scanning report to its infected messages:

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

---- or ----

text.zip
register_.zip
header_.zip
register.zip
text_.zip
help-text.zip
patch_.zip
indictment_cit.zip
text-.zip
 

Followed by:

*-*  Anti-Virus Service  *-* http://www.   

where <domain> is the domain name of a recipient.

The worm does not use any exploits to start its file automatically on a recipient's system.

Deactivation

The worm does not infect a computer if the file with the 'xcvfpokd.tqa' name is present on a hard drive.

Detection

Sober.K worm is detected with the following FSAV updates:

Detection Type: PC

Database: 2005-02-21_01

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