Email-Worm.Win32.Tettona

Technical Details

This is the worm virus spreading via the Internet being attached to infected
emails. The worm also has backdoor routine.

The worm itself is Windows PE EXE file about 35Kb of length (compressed by
Petite, decompressed size – about 75Kb), written in Microsoft Visual C++.

The texts and attached file names in infected messages are different, they depend
on current date and Italian language support:

Subjects are:

Incredible..
Incredibile..
Urgente! (vedi allegato)
Qualsiasi cosa fai,falla al meglio.

The message body begins with “Hello,” or “Ciao,” text, then Bodies are:

 see this interesting file.
 okkio all'allegato ;-)
 devi assolutamente vedere il file che ti ho allegato.
 apri subito l'allegato,e' MOLTO interessante.

The message body is completed with "A presto..." or "Bye." text.

Attached files:

   tettona.exe
   euro.exe
   tattoo.exe

The worm activates from infected email only in case a user clicks on attached
file. The worm then installs itself to the system, runs spreading routine and
backdoor.

Installing

While installing the worm copies itself to Windows directory with the
DLLMGR32.EXE name and registers that file in system registry auto-run key:

HKLMSoftwareMicrosoftWindowsCurrentVersionRun
DllManager = %windir%dllmgr32.exe

The worm then displays fake error message:

 Error
  VBRUN49.DLL not found!

Spreading

To send infected messages the worm uses direct connection to default SMTP
server, then opens WAB database (Windows Address Book) and sends messages to
all addresses found in there.

Backdoor

The backdoor procedure opens connection on port 5001 and listens to the "master". Then it processes following instructions:

 "HELO" - replies with "Hello, guy" text
 "SCAN" - scans all directories and reports dir/files in there (like remote DIR command)
 "EXEC" - runs specified file
 "UNINST" - removes itself from the system, including registry "Run" key.
 "VIEW" - displays to "master" specified file
 "DOWN" - downloads to "master" specified file

Payload

On January 12th the worm displays the message:

 Hello,

  Ciao,
  il tuo computer � infettato dal virus Fral�.
  Certo che devi essere proprio un pirlone,
  per esserti fatto fregare dal mio stupidissimo worm.
  Va b�,v�,non ti preoccupare,oggi non sono in vena di cattiverie,
  ed � anche un giorno festivo per me.

  Buona giornata..
  by 4nt4R35