Threat Description

Sober.E

Details

Aliases: Sober.E, I-Worm.Sober.e, W32/Sober.E@mm, W32.Sober.E@mm
Category: Malware
Type: Worm
Platform: W32

Summary


A new Sober.E worm was found in Germany on Sunday March 28th, 2004. The worm replaces the 'From:' filed so the infected email looks like it comes from @gmx.net or @gmx.de address. The size of the worm's file is 30720 bytes (PIF file) or 30866 bytes (ZIP archive).



Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

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

Contact Support

For further assistance, 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 PE executable 30720 bytes long packed with a modified version of UPX file compressor. The worm has its own SMTP engine that it uses to send out infected e-mail messages.

The worm changes one byte at offset 0xA0 in its file upon installation to system, but the file it sends out is unchanged.

Some of the worm's text strings are encrypted and they are decrypted only before being used.

Installation to system

When the worm's file is started on a clean system, it opens Paintbrush or Microsoft Paint application as a disguise.

Then the worm installs itself to system. It copies itself to Windows System folder once, with a semi-randomly generated name and creates 2 startup keys for this file in System Registry. The worm uses the following fixed text strings to generate the name of its file and the name of the startup key:

sys  host  dir  explorer  win  run  log  32  disc  crypt  data  diag  spool  service  smss32  

The worm creates a file named WINRUN32.DLL, where it stores all e-mail addresses harvested from an infected computer. The worm also creates 2 empty files in the same folder:

zmndpgwf.kxx  bcegfds.lll  

Additionally the worm creates 2 mime-encoded copies of its executable file and a ZIP archive in Windows System folder with the following names:

msWord.wrd  MsHelp32.dat  

The worm creates 2 startup Registry keys its semi-randomly named file in System Registry:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce]  

The subkey name that is created by the worm is semi-randomly generated too. The value of a subkey is the path the worm's file in Windows System folder.

Spreading in e-mails.

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

ini  log  mdb  tbb  abd  adb  pl  abx  rtf  doc  xls  txt  wab  eml  php  asp  shtml  dbx  

The worm saves all found e-mail addresses to WINRUN32.DLL file located in Windows System folder. This is an ASCII file, not a binary file.

Sober.E worm spreads itself in e-mails as an executable attachment or inside a ZIP archive. The worm uses the following strings as the subject line:

Hi  hi  Hi :-)  Ok :-)  OK OK  Ok ok OK!  Hey!  hey?  HEY  

The message body can contain the following strings:

thx  Thx!  THX  ;-)  ha!  HA  yo!  lol  LoL  LOL  Yo!  

The attachment name can consist of the following strings and a randomly generated number:

text  read  Graphic-doc  document  worm  

The attachment has either PIF or ZIP extension. The worm's executable file name inside the archives that we've received so far is:

Graphic_Textdocument.pif  

To send e-mails the worm uses the following mail servers:

mail.gmx.net  mail.gmx.de  

The worm fakes the sender's e-mail address. The fake address is composed by the worm from the following strings:

aRuder  g.rulers  S.Serger  Dude-X777  Nicole.Pam  R.Summer  T.Welder  Susan.Ewing  E.Ruders  Blond.Sybil  Michelle.Horn  Sabine.S-1977  E.Juller  Pamela-S  J.Moders  Regina-1978  BMueller4  Elsbeth.Sinker  Thomas.Schmahler  Nikki.1978  D.Rotter  Patricia.1979  S.Loltke  Patty.Geldorf  H.Molma  Birgit.Muse  Peter.Selders  Johanna.1980  Nicole.Gellert  R.Niere  P.Schulz1  Kalif.Rent  Herbert.Weed  FParker  Samatha.Kelis  Kate.Lee  Bibi.Besen  Julia.Witt1  Alexander.Bendher  Rosemarie.Hetter  A.Rebert  Elke.Duerr  D.Winter1  Angelika.Neum  A.Kempen  KevinEder  Susan.Leet  Friedhelm.alt  Seth.Liveima  Eileen.Leen  D.Augustam  B.Kaine  MikeLord  Kathe.Meet  Marie.Dreher  Tom.Schon  Lisa.Redfield  R.Kleinmaurer  A.Mack1  Jundel  b.sieber006  Ulrike.Falkner  C.Poller  

The following domain names are selected for the fake sender's address:

@gmx.net  @gmx.de  

The worm avoids sending infected messages to e-mail addresses that contain any of the following:

bigfoot  hotmail  online  web  accor  yahoo  gmx  aol  msn  
Additional information

Sober.E worm constantly checks a hard drive for the presence of the file named ZHCARXXI.VVX. If this file is found, the worm unloads itself from memory. Also if this file is present on a hard disk during the worm's installation process, the worm does not copy itself to a hard drive.

The worm can download and run an executable file from the following websites:

home.acror.de  people.freenet.de  

The name of the downloaded file is:

ndhaqqth.exe  

The worm tries to contact several NTP servers that are hardcoded it its body:

Rolex.Peachnet.edu  ntps1-1.cs.tu-berlin.de  ntp2.fau.de  ptbtime2.ptb.de  time.nrc.ca  ntp.metas.ch  ntps1-0.cs.tu-berlin.de  ntp0.fau.de  timelord.uregina.ca  ntp-1.ece.cmu.edu  ptbtime1.ptb.de  time.ien.it  ntp3.fau.de  time.chu.nrc.ca  clock.psu.edu  ntp1.fau.de  


Detection


Detection of Sober.E worm is available in the following FSAV updates:

Detection Type: PC
Database: 2004-03-28_05



Description Details: Katrin Tocheva, March 28th, 2004
Technical Details:Alexey Podrezov; March 28th, 2004
Description Last Modified: Alexey Podrezov; March 29th, 2004


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