Worm/Mytob.CL - Worm

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Summary

Full description

Statistics

Virus:	Worm/Mytob.CL
Date discovered:	02/05/2005
Type:	Worm
In the wild:	Yes
Reported Infections:	Medium
Distribution Potential:	Medium to high
Damage Potential:	Medium
Static file:	No
File size:	~70.000 Bytes
IVDF version:	6.30.00.149 - Mon, 02 May 2005 14:33 (GMT+1)

General Methods of propagation:
   • Email
   • Local network

Aliases:
   • Mcafee: W32/Mytob.gen@MM
   • Kaspersky: Net-Worm.Win32.Mytob.gen
   • F-Secure: Net-Worm.Win32.Mytob.gen
   • Sophos: W32/Mytob-DX
   • Panda: W32/Mytob.GM
   • Grisoft: I-Worm/Mytob.DM
   • Eset: Win32/Mytob.BO
   • Bitdefender: Win32.Worm.Mytob.CR

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
   • Third party control

Files It copies itself to the following locations:
   • %SYSDIR%\winnet32.exe
   • %SYSDIR%\taskmgr32.exe
   • C:\funny_pic.scr
   • C:\see_this!!.scr
   • C:\my_photo2005.scr

The following files are created:

– A file that is for temporary use and it might be deleted afterwards:
   • %TEMPDIR%\tmp%hex number%.tmp

– C:\xmsnn.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]
   • WINTASK32 = taskmgr32.exe

– [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices]
   • WINTASK32 =taskmgr32.exe

– [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   • WINTASK32 = taskmgr32.exe

The following registry keys are added:

– [HKCU\Software\Microsoft\OLE]
   • WINTASK32 = taskmgr32.exe

– [HKCU\SYSTEM\CurrentControlSet\Control\Lsa]
   • WINTASK32 = taskmgr32.exe

– [HKLM\SOFTWARE\Microsoft\Ole]
   • WINTASK32 = taskmgr32.exe

– [HKLM\SYSTEM\CurrentControlSet\Control\Lsa]
   • WINTASK32 = taskmgr32.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:
   • Good day
   • hello
   • Mail Delivery System
   • Mail Transaction Failed
   • Server Report
   • Status
   • Error

Furthermore the subject line could contain random letters.

Body:
– 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.

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

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

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

The email may look like one of the following:

Mailing Search addresses:
It searches the following files for email addresses:
   • txt
   • htmb
   • shtl
   • php
   • asp
   • dbx
   • tbb
   • adb
   • wab

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

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:
   • aol.com
   • msn.com
   • yahoo.com
   • juno.com
   • fbi.gov
   • cia.gov

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

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:
   • mx.
   • mail.
   • smtp.
   • mx1.
   • mxs.
   • mail1.
   • relay.
   • ns.
   • gate.

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 Exploits:
– MS03-026 (Buffer Overrun in RPC Interface)
– 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: xtg.q3w.org
Port: 6667
Channel: #xmsn
Nickname: [I]%random character string%
Password: squadron

– 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
    • Restart system

Hosts The host file is modified as explained:

– In this case already existing entries remain unmodified.

– 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:

– taskmgr32.exe on TCP port 10089 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.

See a brief description here.

Description inserted by Andrei Gherman on Fri, 05 Oct 2007 13:46 (GMT+1)
Description updated by Andrei Gherman on Fri, 05 Oct 2007 14:20 (GMT+1)

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