Analysis by: Jimelle Monteser
ALIASES:

Worm:VBS/Dunihi.A (Microsoft),VBS/Autorun.aafq (NAI), VBS/Agent.NDE worm (NOD32), VBS.Runauto (Norton)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives via removable drives. It 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 copies of itself in all removable drives.

  TECHNICAL DETAILS

File Size: 33,440 bytes
File Type: VBS
Memory Resident: Yes
Initial Samples Received Date: 04 Jul 2013

Arrival Details

This worm arrives via removable drives.

It 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:

  • %User Temp%{malware filename}.vbs

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{malware filename} = "wscript.exe//B"%User Temp%{malware filename}.vbs""

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{malware filename} = "wscript.exe//B"%User Temp%{malware filename}.vbs""

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{malware filename}.vbs

(Note: %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.)

Propagation

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

  • {Removable Drive Letter}:\{malware filename}.vbs

It drops copies of itself in all removable drives.

Other Details

This worm connects to the following possibly malicious URL:

  • http://lovesyr.{BLOCKED}.s.net:8844

NOTES:

It drops the following shortcut pointing to its copy in all removable drive:

  • {Removable Drive Letter}:\{user files}.lnk

It then sets the attributes of the user files to Hidden.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.142.03
FIRST VSAPI PATTERN DATE: 08 Jul 2013
VSAPI OPR PATTERN File: 10.143.00
VSAPI OPR PATTERN Date: 09 Jul 2013

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

Scan your computer with your Trend Micro product and note files detected as VBS_DUNIHI.AD

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware filename} = "wscript.exe//B"%User Temp%{malware filename}.vbs""
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware filename} = "wscript.exe//B"%User Temp%{malware filename}.vbs""

Step 5

Search and delete these files

[ Learn More ]
There may be some 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.
  • %User Temp%{malware filename}.vbs
  • %User Startup%\{malware filename}.vbs
  • {Removable Drive Letter}:\{user files}.lnk

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_DUNIHI.AD. 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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