Virus:Worm/Mytob.CR
Date discovered:07/05/2005
Type:Worm
In the wild:Yes
Reported Infections:Low
Distribution Potential:Medium to high
Damage Potential:Medium
Static file:Yes
File size:52.961 Bytes
MD5 checksum:c425d71833491f881ec33034d59ca504
VDF version:6.30.00.161

 General Methods of propagation:
   • Email
   • Local network


Aliases:
   •  Kaspersky: Net-Worm.Win32.Mytob.t
   •  TrendMicro: WORM_MYTOB.FK
   •  Sophos: W32/Mytob-E
   •  VirusBuster: I-Worm.Mytob.GD
   •  Eset: Win32/Mytob.ET
   •  Bitdefender: Win32.Worm.Mytob.T


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


Side effects:
   • Blocks access to security websites
   • Drops a malicious file
   • Uses its own Email engine
   • Registry modification
   • Makes use of software vulnerability
   • Third party control

 Files It copies itself to the following locations:
   • %SYSDIR%\task32.exe
   • C:\funny_pic.scr
   • C:\see_this!!.scr
   • C:\my_photo2005.scr



It deletes the initially executed copy of itself.



The following file is created:

– C:\hellmsn.exe Furthermore it gets executed after it was fully created. Further investigation pointed out that this file is malware, too. Detected as: Worm/Mytob.F.1

 Registry The following registry keys are continuously in an infinite loop added in order to run the processes after reboot.

–  HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   • "WsTask" = "task32.exe"

–  HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
   • "WsTask" = "task32.exe"

–  HKCU\Software\Microsoft\Windows\CurrentVersion\Run
   • "WsTask" = "task32.exe"



The following registry keys are added:

– HKCU\Software\Microsoft\OLE
   • "WsTask" = "task32.exe"

– HKLM\SOFTWARE\Microsoft\Ole
   • "WsTask" = "task32.exe"

– HKCU\SYSTEM\CurrentControlSet\Control\Lsa
   • "WsTask" = "task32.exe"

– HKLM\SYSTEM\CurrentControlSet\Control\Lsa
   • "WsTask" = "task32.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)
– Generated addresses


Subject:
One of the following:
   • %random character string%
   • Error
   • Good day
   • hello
   • Mail Delivery System
   • Mail Transaction Failed
   • Server Report
   • Status



Body:
–  In some cases it may be empty.

 
The body of the email is one of the lines:
   • %random character string%
   • Here are your banks documents.
   • Mail transaction failed. Partial message is available.
   • The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
   • The message contains Unicode characters and has been sent as a binary attachment.
   • The original message was included as an attachment.


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

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

    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:
   • adb; asp; dbx; doc; htm; php; sht; tbb; tmp; txt; wab


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

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
   • cia.gov
   • fbi.gov
   • juno.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;
      iana; ibm.com; icrosof; icrosoft; ietf; info; inpris; isc.o; isi.e;
      kernel; linux; listserv; math; mit.e; mozilla; 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.
   • mail.
   • mail1.
   • mx.
   • mx1.
   • mxs.
   • ns.
   • relay.
   • smtp.

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


Exploit:
– MS04-011 (LSASS Vulnerability)


IP address generation:
It creates random IP addresses while it keeps the first two octets from its own address. Afterwards it tries to establish a connection with the created addresses.


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: dns.sdf2sd**********
Port: 8080
Channel: #helltest
Nickname: [I]%random character string%
Password: vicecity



– This malware has the ability to collect and send the following information:
    • Malware uptime


– Furthermore it has the ability to perform actions such as:
    • Download file
    • Execute file
    • Updates itself

 Hosts The host file is modified as explained:

– In this case existing entries are deleted.

– Access to the following domains is effectively blocked:
   • www.symantec.com; securityresponse.symantec.com; symantec.com;
      www.sophos.com; sophos.com; www.mcafee.com; mcafee.com;
      liveupdate.symantecliveupdate.com; www.viruslist.com; viruslist.com;
      viruslist.com; f-secure.com; www.f-secure.com; kaspersky.com;
      www.avp.com; www.kaspersky.com; avp.com; www.networkassociates.com;
      networkassociates.com; www.ca.com; ca.com; mast.mcafee.com;
      my-etrust.com; www.my-etrust.com; download.mcafee.com;
      dispatch.mcafee.com; secure.nai.com; nai.com; www.nai.com;
      update.symantec.com; updates.symantec.com; us.mcafee.com;
      liveupdate.symantec.com; customer.symantec.com; rads.mcafee.com;
      trendmicro.com; www.microsoft.com; www.trendmicro.com




The modified host file will look like this:


 Backdoor The following port is opened:

– %SYSDIR%\task32.exe on TCP port 10087 in order to provide an FTP server.

 Miscellaneous Mutex:
It creates the following Mutex:
   • H-E-L-L-B-O-T

 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 Wednesday, March 15, 2006

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