WORM_MYTOB.JX

Malware type: Worm

Aliases: Net-Worm.Win32.Mytob.cu (Kaspersky), W32/Mytob.gen@MM (McAfee), W32.Mytob@mm (Symantec), HEUR/Malware (Avira), W32/Forbot-FK (Sophos),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows NT, 2000, XP

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

High

Distribution potential:

High

Description: 

Similar to other MYTOB variants, this memory-resident worm propagates by sending a copy of itself as an attachment to an email message, which it sends to target recipients using its own Simple Mail Transfer Protocol (SMTP) engine. Using its own SMTP mail engine makes it easier for this worm to send out email messages, while maintaining transparency on the affected system.

The email it sends out has the following details:

Subject: (any of the following)
• *DETECTED* Online User Violation
• *WARNING* Your email account is suspended
• Email Account Suspension
• Important Notification
• Members Support
• Notice of account limitation
• Security measures
• Warning Message: Your services near to be closed.
• We have suspended your account
• You are banned!!!
• Your Account is Suspended
• Your Account is Suspended For Security Reasons

Message body: (composed using any of the following)
• Dear {random} Member,
• We have temporarily suspended your email account {random}.
This might be due to either of the following reasons:
1. A recent change in your personal information (i.e. change of address).
2. Submiting invalid information during the initial sign up process.
3. An innability to accurately verify your selected option of subscription due to an internal error within our processors.
• Your e-mail account was used to send a huge amount of unsolicited spam messages during the recent week. If you could please take 5-10 minutes out of your online experience and confirm the attached document so you will not run into any future problems with the online service.
• Some information about your {random} account is attached.
• See the attached details to reactivate your {random} account.
• Sincerely,The {random} Support Team
• Virtually yours,
• The {random} Support Team

Attachment: (any of the following file names)
• account-details
• account-report
• account-info
• email-details
• information
• important details
• readme

(with any of the following extensions)
• BAT
• CMD
• EXE
• PIF
• SCR
• ZIP

The following is a sample email that this worm sends out:

Sample email of WORM_MYTOB.JX

For more details about the email propagation routine of this worm, please click here.

This worm also propagates by dropping a copy of itself in accessible network shares. It accesses an affected system by logging on using the account of the currently logged-on user.

Furthermore, it also propagates across networks by taking advantage of the Windows LSASS vulnerability. The mentioned vulnerability is discussed in detail in the following Web page:

This worm has backdoor capabilities. It opens a random port, which allows a remote user to perform malicious commands on the affected machine. The said routine provides remote users virtual control over affected systems, thus compromising system security.

For additional information about this threat, see:

Description created: Aug. 23, 2005 6:05:13 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 94,359 Bytes

Ports used: Random

Initial samples received on: Aug 23, 2005

Vulnerability used:  (MS04-011) Security Update for Microsoft Windows (835732)

Payload 1: Compromises system security

Details:

Installation and Autostart Technique

Upon execution, this worm drops a copy of itself as MAILINFO.EXE in the Windows folder. It then creates the following registry entries to ensure its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Help = "mailinfo.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunServices
Windows Help = "mailinfo.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
Windows Help = "mailinfo.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Help = "mailinfo.exe"

Network Propagation and Exploits

This memory-resident worm propagates by dropping a copy of itself in accessible network shares. It accesses an affected system by logging on using the account of the currently logged-on user.

It also takes advantage of the Windows LSASS vulnerability to propagate across networks. The mentioned vulnerability is discussed in detail in the following Web page:

Email Propagation

This worm propagates by sending a copy of itself as an attachment to email messages, which it sends to target recipients, using its own Simple Mail Transfer Protocol (SMTP) engine.

It also searches for available SMTP servers by checking the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts

The email it sends out has the following details:

Subject: (any of the following)
• *DETECTED* Online User Violation
• *WARNING* Your email account is suspended
• Email Account Suspension
• Important Notification
• Members Support
• Notice of account limitation
• Security measures
• Warning Message: Your services near to be closed.
• We have suspended your account
• You are banned!!!
• Your Account is Suspended
• Your Account is Suspended For Security Reasons

Message body: (composed using any of the following)
• Dear {random} Member,
• We have temporarily suspended your email account {random}.
This might be due to either of the following reasons:
1. A recent change in your personal information (i.e. change of address).
2. Submiting invalid information during the initial sign up process.
3. An innability to accurately verify your selected option of subscription due to an internal error within our processors.
• Your e-mail account was used to send a huge amount of unsolicited spam messages during the recent week. If you could please take 5-10 minutes out of your online experience and confirm the attached document so you will not run into any future problems with the online service.
• Some information about your {random} account is attached.
• See the attached details to reactivate your {random} account.
• Sincerely,The {random} Support Team
• Virtually yours,
• The {random} Support Team

Attachment: (any of the following file names)
• account-details
• account-report
• account-info
• email-details
• information
• important details
• readme

(with any of the following extensions)
• BAT
• CMD
• EXE
• PIF
• SCR
• ZIP

The following is a sample email it sends out:

Sample email of WORM_MYTOB.JX

It gathers target email addresses from the Windows Address Book (WAB) and Temporary Internet Files folder.

It also spoofs the From field by using the following common names appended with a domain name from previously gathered email addresses:

  • accounts
  • administrator
  • andrew
  • brenda
  • brent
  • brian
  • britney
  • claudia
  • david
  • debby
  • george
  • helen
  • james
  • jerry
  • jimmy
  • julie
  • kevin
  • linda
  • lolita
  • madmax
  • mail
  • maria
  • michael
  • peter
  • register
  • robert
  • sandra
  • smith
  • steve

It avoids email addresses containing any of the following substrings:

  • abuse
  • accoun
  • admin
  • anyone
  • certific
  • contact
  • feste
  • gold-certs
  • google
  • icrosoft
  • linux
  • listserv
  • nobody
  • noone
  • nothing
  • ntivi
  • postmaster
  • privacy
  • rating
  • samples
  • secur
  • service
  • somebody
  • someone
  • submit
  • support
  • the.bat
  • webmaster

It also avoids email addresses with the following strings in the domain name:

  • acketst
  • arin.
  • berkeley
  • borlan
  • example
  • google
  • hotmail
  • ibm.com
  • icrosof
  • inpris
  • isc.o
  • isi.e
  • kernel
  • linux
  • mit.e
  • mozilla
  • mydomai
  • nodomai
  • panda
  • rfc-ed
  • ripe.
  • ruslis
  • secur
  • sendmail
  • sopho
  • tanford.e
  • usenet
  • utgers.ed

It also queries the message exchange servers of gathered email addresses by prepending the domain names with the following strings:

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

Backdoor Capabilities

This worm also has backdoor capabilities. It opens a random port, and then connects to the Internet Relay Chat (IRC) server. It then joins a specific IRC channel where it receives the following commands from a remote malicious user:

  • Download files
  • Execute files
  • Perform other IRC commands
  • Restart system
  • Set up FTP server using random port

Other Details

This worm runs on Windows NT, 2000, and XP.

Analysis By: Adrian J. Ayala

Revision History:

First pattern file version: 5.548.02
First pattern file release date: Sep 17, 2008

SOLUTION


Minimum scan engine version needed: 6.810

Pattern file needed: 5.549.00

Pattern release date: Sep 17, 2008


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Terminating the Malware Program

This procedure terminates the running malware process.

If the process you are looking for is not in the list displayed by Task Manager, proceed to the succeeding solution set.

  1. Open Windows Task Manager.
    Press CTRL%20SHIFT%20ESC, then click the Processes tab.
  2. In the list of running programs*, locate the process:
    MAILINFO.EXE
  3. Select the malware process, then press either the End Task or the End Process button, depending on the version of Windows on your system.
  4. To check if the malware process has been terminated, close Task Manager, and then open it again.
  5. Close Task Manager.

*NOTE: If you were not able to terminate the malware process as described in the previous procedure, restart your system.

Editing the Registry

This malware modifies the system's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

  1. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
  2. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
  3. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and 2003

Removing Autostart Entries from the Registry

Removing autostart entries from the registry prevents the malware from executing at startup.

If the registry entries below are not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate and delete the entry:
    Windows Help = "mailinfo.exe"
  4. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>RunServices
  5. In the right panel, locate and delete the entry:
    Windows Help = "mailinfo.exe"
  6. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>Run
  7. In the right panel, locate and delete the entry:
    Windows Help = "mailinfo.exe"
  8. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>RunOnce
  9. In the right panel, locate and delete the entry:
    Windows Help = "mailinfo.exe"
  10. Close Registry Editor.

Important Windows XP Cleaning Instructions

Users running Windows XP must disable System Restore to allow full scanning of infected systems.

Users running other Windows versions can proceed with the succeeding procedure set(s).

Running Trend Micro Antivirus

Scan your system with Trend Micro antivirus and delete files detected as WORM_MYTOB.JX. To do this, Trend Micro customers must download the latest virus pattern file and scan their system. Other Internet users can use HouseCall, Trend Micro's online virus scanner.

Applying Patch

This malware exploits known vulnerabilities in Windows. Download and install the fix patch supplied by Microsoft. Refrain from using this product until the appropriate patch has been installed. Trend Micro advises users to download critical patches upon release by vendors.




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