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WORM_COSMU.MC

October 09, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Trojan.Win32.Cosmu.bbx (Kaspersky); TrojanDownloader:Win32/Lopstonc.A (Microsoft)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives


This worm arrives via removable drives. It may be downloaded by other malware/grayware/spyware from remote sites. It may be unknowingly downloaded by a user while visiting malicious websites.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

112,128 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Aug 2011

Payload:

Drops files

Arrival Details

This worm arrives via removable drives.

It may be downloaded by other malware/grayware/spyware from remote sites.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This worm drops the following non-malicious files:

  • %System%\Ntimnage.jpg - non-malicious image
  • %System%\nu - contains malware installation log

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following copies of itself into the affected system:

  • %System%\msiregnv.exe
  • %User Startup%\georgia.jpg.exe
  • d:/foto005.jpg.exe
  • e:/download001.jpg.exe
  • f:/samleb.jpg.exe
  • g:/sorsi.jpg.exe
  • h:/image32.jpg.exe
  • i:/pano001.jpg.exe
  • j:/windo.jpg.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • MyOwnMutex

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
svñhost = "%System%/msiregnv.exe"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • Image0001.jpg.exe

Dropping Routine

This worm drops the following files:

  • %System%\sis32.bat - detected as BAT_COSMU.MC

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.366.12

FIRST VSAPI PATTERN DATE:

24 Aug 2011

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_COSMU.MC

    BAT_COSMU.MC

Step 3

Identify and terminate files detected as WORM_COSMU.MC

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • %System%\Ntimnage.jpg
  • %System%\nu

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • svñhost = %System%/msiregnv.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_COSMU.MC. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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