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Date discovered:11/04/2005
In the wild:Yes
Reported Infections:Low
Distribution Potential:Medium to high
Damage Potential:Medium
Static file:Yes
File size:65.536 Bytes
MD5 checksum:380F24D0E0AD7C5713C4C3244C55D3CD
VDF version:

 General Methods of propagation:
   • Email
   • Local network

   •  Symantec: W32.Mytob.AG@mm
   •  Kaspersky: Net-Worm.Win32.Mytob.u
   •  TrendMicro: WORM_MYTOB.AC
   •  Sophos: W32/MyDoom-AJ
   •  Grisoft: I-Worm/Mytob.AV
   •  VirusBuster: iworm I-Worm.Mytob.BC1
   •  Eset: Win32/Mytob.Y worm
   •  Bitdefender: Win32.Worm.Mytob.AF

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

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

 Files It copies itself to the following locations:
   • %SYSDIR%\rnathchk.exe
   • C:\my_picture.scr
   • C:\pic.scr
   • C:\see_this!

 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]
   • "RealPlayer Ath Check"="rnathchk.exe"

–  [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices]
   • "RealPlayer Ath Check"="rnathchk.exe"

–  [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   • "RealPlayer Ath Check"="rnathchk.exe"

The following registry keys are added:

– [HKCU\Software\Microsoft\OLE]
   • "RealPlayer Ath Check"="rnathchk.exe"

– [HKCU\SYSTEM\CurrentControlSet\Control\Lsa]
   • "RealPlayer Ath Check"="rnathchk.exe"

– [HKLM\SOFTWARE\Microsoft\Ole]
   • "RealPlayer Ath Check"="rnathchk.exe"

– [HKLM\SYSTEM\CurrentControlSet\Control\Lsa]
   • "RealPlayer Ath Check"="rnathchk.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:

The sender address is spoofed.

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

One of the following:
   • ERROR
   • hello
   • Mail Transaction Failed
   • Server Report
   • Status

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

–  In some cases it may contain random characters.
The body of the email is one of the lines:
   • Here are your banks documents.
   • The original message was included as an attachment.
   • 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.
   • Mail transaction failed. Partial message is available.

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
   • %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 email looks like the following:

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

Address generation for TO and FROM fields:
To generate addresses it uses the following strings:
   • adam; alex; andrew; anna; bill; bob; 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:

Avoid addresses:
It does not send emails to addresses containing one of the following strings:
   • -._!; -._!@; .edu; .gov; .mil; accoun; acketst; admin; anyone; arin.;
      avp; be_loyal:; berkeley; borlan; bsd; bsd; bugs; certific; contact;
      example; feste; fido; foo.; fsf.; gnu; gold-certs; google; google;
      gov.; help; iana;; icrosof; icrosoft; ietf; info; inpris;
      isc.o; isi.e; kernel; linux; 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; unix; usenet;
      utgers.ed; webmaster; 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.

It makes use of the following 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.
The downloaded file is stored on the compromised machine as: %SYSDIR%\wtfhe.exe

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

Server: spm.slo-partija.**********
Port: 48275
Server password: 57284
Channel: #hb2
Nickname: [I]%random character string%
Password: sp4m

Server: spm.gobice.**********
Port: 48275
Server password: 57284
Channel: #hb2
Nickname: [I]%random character string%
Password: spam

Server: egwf.wegberobpk.**********
Port: 48275
Server password: 57284
Channel: #hb2
Nickname: [I]%random character string%
Password: spam

– 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:
    • disconnect from IRC server
    • Download file
    • Execute file
    • Updates itself

 Hosts The host file is modified as explained:

– In this case already existing entries remain unmodified.

– Access to the following domains is effectively blocked:

 Backdoor The following port is opened:

– rnathchk.exe on TCP port 36276 in order to provide an FTP server.

 Miscellaneous Mutex:
It creates the following Mutex:

 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 the following runtime packer:
   • FSG 1.33

Description inserted by Iulia Diaconescu on Friday, October 13, 2006
Description updated by Iulia Diaconescu on Wednesday, October 18, 2006

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