Virus:Worm/Mytob.U
Date discovered:04/04/2005
Type:Worm
In the wild:Yes
Reported Infections:Low
Distribution Potential:Medium to high
Damage Potential:Medium
Static file:Yes
File size:46.687 Bytes
MD5 checksum:f558083b9778eecd17657fbd4e8b958d
VDF version:6.30.00.62

 General Methods of propagation:
   • Email
   • Local network


Aliases:
   •  Mcafee: W32/Mytob.gen@MM
   •  Kaspersky: Net-Worm.Win32.Mytob.c
   •  Sophos: W32/Mytob-C
   •  Grisoft: I-Worm/Mytob.C
   •  VirusBuster: I-Worm.Mytob.V
   •  Eset: Win32/Mytob.D
   •  Bitdefender: Win32.Worm.Mytob.C


Platforms / OS:
   • Windows 95
   • Windows 98
   • Windows 98 SE
   • Windows NT
   • Windows ME
   • Windows 2000
   • Windows XP
   • Windows 2003


Side effects:
   • Uses its own Email engine
   • Registry modification
   • Makes use of software vulnerability
   • Third party control

 Files It copies itself to the following location:
   • %SYSDIR%\wfdmgr.exe

 Registry The following registry keys are added in order to run the processes after reboot:

– HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   • "LSA"="wfdmgr.exe"

– HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
   • "LSA"="wfdmgr.exe"

– HKCU\Software\Microsoft\Windows\CurrentVersion\Run
   • "LSA"="wfdmgr.exe"



The following registry keys are added:

– HKCU\Software\Microsoft\OLE
   • "LSA"="wfdmgr.exe"

– HKCU\SYSTEM\CurrentControlSet\Control\Lsa
   • "LSA"="wfdmgr.exe

– HKLM\SOFTWARE\Microsoft\Ole
   • "LSA"="wfdmgr.exe"

– HKLM\SYSTEM\CurrentControlSet\Control\Lsa
   • "LSA"="wfdmgr.exe"

 Email It contains an integrated SMTP engine in order to send emails. A direct connection with the destination server will be established. The characteristics are described in the following:


From:
The sender address is spoofed.
Generated addresses. Please do not assume that it was the sender's intention to send this email to you. He might not know about his infection or might not even be infected at all. Furthermore it is possible that you will receive bounced emails telling you that you are infected. This might also not be the case.


To:
– Email addresses found in specific files on the system.
– Email addresses gathered from WAB (Windows Address Book)


Subject:
One of the following:
   • hello
   • hi
   • Error
   • Status
   • Server Report
   • Mail Transaction Failed
   • Mail Delivery System

In some cases the subject might also be empty.
Furthermore the subject line could contain random letters.


Body:
–  In some cases it may be empty.

 
The body of the email is one of the lines:
   • Mail transaction failed. Partial message is available.
   • The message contains Unicode characters and has been sent as a binary attachment.
   • The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
   • test


Attachment:
The filenames of the attachments is constructed out of the following:

–  It starts with one of the following:
   • body
   • message
   • test
   • data
   • file
   • text
   • doc
   • readme
   • document

    The file extension is one of the following:
   • bat
   • cmd
   • exe
   • scr
   • pif
   • zip

The attachment is a copy of the malware itself.

The attachment is an archive containing a copy of the malware itself.



The email looks like the following:


 Mailing Search addresses:
It searches the following files for email addresses:
   • wab
   • adb
   • tbb
   • dbx
   • asp
   • php
   • sht
   • htm


Address generation for TO and FROM fields:
To generate addresses it uses the following strings:
   • %random character string%; sandra; linda; julie; jimmy; jerry;
      helen; debby; claudia; brenda; anna; alice; brent; adam; ted; fred;
      jack; bill; stan; smith; steve; matt; dave; dan; joe; jane; bob;
      robert; peter; tom; ray; mary; serg; brian; jim; maria; leo; jose;
      andrew; sam; george; david; kevin; mike; james; michael; alex; john

It combines this with domains from the following list or from addresses found in files on the system

The domain is one of the following:
   • hotmail.com
   • yahoo.com
   • msn.com
   • aol.com


Avoid addresses:
It does not send emails to addresses containing one of the following strings:
   • .edu; .gov; .mil; abuse; accoun; acketst; admin; anyone; arin.; avp;
      be_loyal:; berkeley; borlan; bsd; bugs; certific; contact; example;
      feste; fido; foo.; fsf.; gnu; gold-certs; google; gov.; help; hotmail;
      iana; ibm.com; icrosof; icrosoft; ietf; info; inpris; isc.o; isi.e;
      kernel; linux; listserv; math; mit.e; mozilla; msn.; mydomai; nobody;
      nodomai; noone; not; nothing; ntivi; page; panda; pgp; postmaster;
      privacy; rating; rfc-ed; ripe.; root; ruslis; samples; secur;
      sendmail; service; site; soft; somebody; someone; sopho; submit;
      support; syma; tanford.e; the.bat; unix; usenet; utgers.ed; webmaster;
      www; you; your


Prepend MX strings:
In order to get the IP address of the mail server it has the ability to prepend the following strings to the domain name:
   • gate.
   • ns.
   • relay.
   • mail1.
   • mxs.
   • mx1.
   • smtp.
   • mail.
   • mx.

 Network Infection In order to ensure its propagation the malware attemps to connect to other machines as described below.


Exploit:
It makes use of the following Exploit:
– MS04-011 (LSASS Vulnerability)


Infection process:
Creates an FTP script on the compromised machine in order to download the malware to the remote location.

 IRC To deliver system information and to provide remote control it connects to the following IRC Server:

Server: 18.xx**********
Port: 13000
Channel: #m-rl1
Nickname: %random character string%
Password: G



– This malware has the ability to collect and send information such as:
    • Malware uptime
    • Information about the network


– Furthermore it has the ability to perform actions such as:
    • Download file
    • Execute file
    • Send emails
    • Start spreading routine
    • Updates itself

 Backdoor The following port is opened:

– %SYSDIR%\wfdmgr.exe on a random TCP port in order to provide an FTP server.

 Miscellaneous Mutex:
It creates the following Mutex:
   • D66

 File details Programming language:
 The malware program was written in MS Visual C++.


Runtime packer:
In order to aggravate detection and reduce size of the file it is packed with a runtime packer.

Description inserted by Irina Boldea on Tuesday, February 28, 2006
Description updated by Irina Boldea on Thursday, March 16, 2006

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