WORM_EMOLD.SB

January 11, 2013
 Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size:

16,384 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 May 2009

Arrival Details

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following copies of itself into the affected system:

  • %Program Files%\Movie Maker\wmv2avi.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

This worm adds the following Image File Execution Options registry entries to automatically execute itself whenever certain applications are run:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
explorer.exe
Debugger = "%Program Files%\Movie Maker\wmv2avi.exe"

Propagation

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

  • system.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
;t
open=system.exe
;t
shellexecute=system.exe
;t
shell\Explore\command=system.exe
;t
shell\Open\command=system.exe
;t
shell=Explore

Other Details

This worm connects to the following possibly malicious URL:

  • {BLOCKED}eavy.cn

  SOLUTION

Minimum Scan Engine:

9.300

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

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 NT\CurrentVersion\Image File Execution Options\explorer.exe
    • Debugger = "%Program Files%\Movie Maker\wmv2avi.exe"

Step 4

Search and delete AUTORUN.INF files created by WORM_EMOLD.SB that contain these strings

[ Learn More ]
[autorun
;t
open=system.exe
;t
shellexecute=system.exe
;t
shell\Explore\command=system.exe
;t
shell\Open\command=system.exe
;t
shell=Explore

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_EMOLD.SB. 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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