WORM_LETUM.A

Malware type: Worm

Aliases: Email-Worm.MSIL.Letum.a (Kaspersky), MSIL/Letum.a@MM (McAfee), MSIL.Letum.A@mm (Symantec), Worm/Letum.A (Avira), W32/Letum-A (Sophos),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

High

Distribution potential:

High

Infection Channel 1 : Propagates via email


Infection Channel 2 : Propagates via newsgroups


Description: 

To get a one-glance comprehensive view of the behavior of this worm, refer to the Behavior Diagram shown below.

WORM_LETUM.A Behavior Diagram

Malware Overview

This worm propagates via email. It searches for available Simple Mail Transfer Protocol (SMTP) servers through the Internet Account Manager. If none is available, it uses the default server mail.primaryhost.org.uk. It then connects to a target SMTP server and sends its copy to five email addresses that it was able to gather from .HTML files found on the affected system.

Users must be wary of the email message this worm sends out because its accompanying attachment is a copy of this worm that, upon execution, transforms the compromised system into a propagation launchpad, which furthers its replication.

It can also propagate via newsgroups. Newsgroups work like virtual bulletin boards in that members subscribed to a particular group can discuss subjects of mutual interest by posting messages and commments. Members can even include attachments to their posts. As such, this worm searches for target newsgroups in available Network News Transfer Protocol (NNTP) servers also through the Internet Account Manager. If none is available, it uses the default NNTP server news.microsoft.com. It then posts a message with an attachment that is actually a copy of itself.

In addition, it displays a message box containing the following text strings:

Title: Name Entry Error
Message:
Dear Pete{BLOCKED}rrie

GeNeTiX is a person not a f**king genetically modified food product. She's not happy you called her that!

Regards

For additional information about this threat, see:

Description created: Apr. 8, 2006 1:19:09 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 32,768 Bytes

Initial samples received on: Apr 8, 2006

Payload 1: Displays a message box

Details:

Installation and Autostart Technique

Upon execution, this memory-resident worm lists all the folders and sub-folders found in C:\, picks one randomly and drops a copy of itself in it with a random file name. It creates the following registry entry to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Letum = "C:\{Malware path and file name}"

It also adds the following registry entry as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Retro
Letum = "C:\{Malware path and file name}"

Propagation via Email

This worm propagates via email. It searches for available Simple Mail Transfer Protocol (SMTP) servers through the Internet Account Manager. If none is available, it uses the default server mail.primaryhost.org.uk.

It then searches for the following registry key to get information as to where its dropped copy is located:

HKEY_LOCAL_MACHINE\SOFTWARE\Retro

Once it finds its dropped copy, it renames the said copy to TEST.EXE and uses it as an attachment to the email messages it sends out.

This worm then connects to its target SMTP server and sends its copy to five email addresses that it was able to gather from .HTML files found on the affected system.

Users must be wary of the email message this worm sends, which may appear as follows:

From: Symantec Security Response [pete{BLOCKED}rrie@symantec.com]

Subject: (any of the following)

• Customer Support
• Re:
• Re:Warning
• Security Response
• Virus Alert
• Virus Report
• Warning!

Message Body:
Dear User,

Due to the high increase of the Letum worm, we have upgraded it to Category B. Please use our attached removal tool to scan and disinfect your computer from the malware.

If you have any comments or questions about this, then please contact us.

Regards

Pete{BLOCKED}rrie
Senior Anti-Virus Researcher / Senior Principal Software Engineer


�1995 - 2006 Symantec Corporation All rights reserved.

Attachment: test.exe

Propagation via Newsgroups

This worm can propagate via newsgroups. Newsgroups work like virtual bulletin boards in that members subscribed to a particular group can discuss subjects of mutual interest by posting messages and commments. Members can even include attachments to their posts. As such, this worm searches for target newsgroups in available Network News Transfer Protocol (NNTP) servers through the Internet Account Manager. If none is available, it uses the default NNTP server news.microsoft.com. It then posts a message with an attachment that is actually a copy of itself.

The message it posts has the following details:

From: pete{BLOCKED}rrie@symantec.com

Newgroups: {newsgroup name}

Subject: (any of the following)

• Customer Support
• Re:Warning
• Security Response
• Virus Alert
• Virus Report
• Warning!

Message Body: (any of the following)
Dear Users

Due to the high increase of the Letum worm, we have upgraded it to Category B. Please use our attached removal tool to scan and disinfect your computer from the malware.

Regards
Security Response
____________________________

Hiya,

I've found this tool a couple of weeks ago, and after using it i was surprised on how good it was on squashing viruses. I wonder if avers know about this? ;)
____________________________

Maybe not but try this, i'm sure it will help you in your fight against malware. The engine it uses isnt to bad, but the searching speed is very fast for such a small size

Other Details

This worm displays a message box containing the following text strings:

Title: Name Entry Error
Message:
Dear Pete{BLOCKED}rrie

GeNeTiX is a person not a f**king genetically modified food product. She's not happy you called her that!

Regards

Affected Platforms

This worm runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Jocelyn D. Racoma

Updated By: Michael de Leon Lactaotao

Revision History:

 
Apr 8, 2006 - Modified Virus Report

SOLUTION


Minimum scan engine version needed: 7.500

Pattern file needed: 3.320.05

Pattern release date: Apr 8, 2006


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:

Identifying the Malware Program

To remove this malware, first identify the malware program.

  1. Scan your computer with your Trend Micro antivirus product.
  2. NOTE the path and file name of all files detected as WORM_LETUM.A.

Trend Micro customers need to download the latest virus pattern file before scanning their computer. Other users can use Housecall, the Trend Micro online virus scanner.

Terminating the Malware Program

This procedure terminates the running malware process. You will need the name(s) of the file(s) detected earlier.

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.
    • On Windows 98, and ME, press
    CTRL%20ALT%20DELETE
    • On Windows NT, 2000, XP, and Server 2003, press
    CTRL%20SHIFT%20ESC, then click the Processes tab.
  2. In the list of running programs*, locate the malware file(s) detected earlier.
  3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
  4. Do the same for all detected malware files in the list of running processes.
  5. To check if the malware process has been terminated, close Task Manager, and then open it again.
  6. Close Task Manager.

*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

On computers running all Windows platforms, if the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure, noting additional instructions. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Editing the Registry

This malware modifies the computer'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 95, Windows 98, and Windows ME
  2. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
  3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
  4. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and Server 2003

Removing Autostart Entries from the Registry

Removing autostart entries from the registry prevents the malware from executing at startup. In this procedure, you will need the name of the file detected earlier.

If the registry entry below is 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 whose data value is the malware path and file name of the file detected earlier.

Removing Other Key from the Registry

  1. Still in Registry Editor, in the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE
  2. In the left panel, locate and delete the key:
    Retro
  3. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

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

Running Trend Micro Antivirus

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

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




Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.