WORM_OTORUN.WSH

 Analysis by: Michael Cabel

 ALIASES:

Worm:Win32/Rorpian (Microsoft); Worm.Win32.AutoRun.cewu (Kaspersky); W32/Autorun.worm.aabl (McAfee)

 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:

Copies itself in all available physical drives, Propagates via removable drives

This worm arrives via removable drives. It may be dropped by other malware.

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:

65,544 bytes

File Type:

DLL

Initial Samples Received Date:

29 Mar 2011

Payload:

Connects to URLs/IPs

Arrival Details

This worm arrives via removable drives.

It may be dropped by other malware.

Installation

This worm drops the following non-malicious file:

  • %User Temp%\srv{random numbers}.ini

(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.)

It uses the following names for the copies it drops:

  • %User Temp%\srv{random numbers}.tmp

(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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\srv{Random Numners}\parameters
servicedll = "\?\globalroot\Device\HarddiskVolume1\%User Temp%\srv{random numbers}.tmp"

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings
ProxyEnable = "0"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Minimal\
srv{random numbers}

Propagation

This worm drops the following copy of itself in all physical and removable drives:

  • setup{random numbers}.fon

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]
Action = Open folder to view files
rundll32.exe setup{random numbers}.fon
shell\open\command = rundll32.exe setup{random numbers}.fon
Icon = %System%\shell32.dll,4
useautoplay = 1

(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.)

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.88.10//srv
  • http://{BLOCKED}.{BLOCKED}.88.10//dll

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.938.01

FIRST VSAPI PATTERN DATE:

29 Mar 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

Identify and delete files detected as WORM_OTORUN.WSH using the Recovery Console

[ 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_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • ProxyEnable = 0

Step 4

Delete this registry key

[ 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\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal
    • srv{random numbers}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • srv{random numbers}

Step 5

Search and delete AUTORUN.INF files created by WORM_OTORUN.WSH that contain these strings

[ Learn More ]
[AutoRun]
Action = Open folder to view files
rundll32.exe setup{random numbers}.fon
shell\open\command = rundll32.exe setup{random numbers}.fon
Icon = %System%\shell32.dll,4
useautoplay = 1

Step 6

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.
  • %User Temp%\srv{random numbers}.ini

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_OTORUN.WSH. 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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