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Email-Worm:W32/Sober.N

Classification

Category: Malware

Type: -

Aliases: Sober.N, Email-Worm.Win32.VB.aj, W32.Sober.N@mm, W32/Sober.o@MM

Summary


Sober.N email worm was found on 19th of April, 2005. It sends itself as an attachment in email messages with English or German texts.

Removal


Automatic action

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

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Technical Details


The worm is written in Visual Basic. The worm's file is a modified UPX packed PE executable about 73 kilobytes long.

The worm sends different types of email messages with English and German texts and an attachment. The attachment is a ZIP archive containing the worm's executable.

The worm composes messages with subject lines such as "I've_got your EMail on my_account!" and "FwD: Ich bin's nochmal" with attachments such as your_text.zip.

Installation to system

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

When the worm's file is run, it copies itself as "services.exe" into the %WinDir%\Config\system\ folder, created by the worm.

Sober.N worm adds startup keys for "services.exe" in System Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
"SystemCheck" = "%WinDir%\Config\system\services.exe"
[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"_SystemCheck" = "%WinDir%\Config\system\services.exe"
 

The worm also creates the following files to installation folder:

zipped.wrm
maddys.xyz
 

'zipped.wrm' contains base64-encoded worm, used in spreading. 'maddsys.xyz' is used to store email addresses.

The worm also writes the following files to system folder:

nonrunso.ber
langeinf.lin
adcmmmmq.hjg
xcvfpokd.tqa
 

These files are used to deactivate previous variants of the worm.

Spreading in emails

The worm sends different types of email messages with English and German texts and its file attached. The attachment is a ZIP archive containing the worm's executable.

Before spreading the worm scans files with certain extensions on all hard disks to harvest email 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 worm ignores email addresses that contain any of the following substrings:

@www
@from.
smtp-
@smtp.
ftp.
.dial.
.ppp.
anyone
@gmetref
sql.
someone
nothing
you@
user@
reciver@
somebody
secure
whatever@
whoever@
anywhere
yourname
mustermann@
mailer-daemon
variabel
noreply
-dav
law2
.qmail@
freeav
@ca.
abuse
winrar
domain.
host.
viren
bitdefender
spybot
detection
ewido.
emsisoft
linux
@foo.
winzip
@example.
bellcore.
@arin
@iana
@avp
icrosoft.
@sophos
@panda
@kaspers
free-av
antivir
virus
verizon.
@ikarus.
@nai.
@messagelab
nlpmail01.
clock
 

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

The worm composes the following messages:

Subjects:

I've_got your EMail on my_account!
FwD: Ich bin's nochmal
 

Body texts:

Hello,
First, Very Sorry for my bad English.
Someone is sending your private emails on my address.
It's probably an email provider error!
At time, I've got over 10 mails on my account, but the recipient are you.
I have copied all the mail text in the windows text-editor for you & zipped then.
Make sure, that this mails don't come in my mail-box again.
bye
Verdammt,,,,
ich hatte vergessen Dir meinen Text mitzuschicken.
Aber bitte nicht woanders darueber Reden, ich wuerde mich dann zu Tode blamieren!
Ich melde mich.
Bis bald ;)
 

Attachments:

your_text.zip
Private-Texte.zip
 

The actual worm executable name inside the attachement is 'mail.document.Datex-packed.exe'.