WORM_SMALL.HYN

 Modified by: Kiyoshi Obuchi

 ALIASES:

Virus:Win32/Small.R (Microsoft); Generic BackDoor.j (McAfee); W32.SillyDC (Symantec); Virus.Win32.Small.r (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Win32.Worm.TRG (FSecure)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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:

106,496 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

09 Mar 2011

Payload:

Drops files, Executes files

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 and executes them:

  • %Windows%\system\svchost.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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

  • %Windows%\system\_sv_CMD_\_U_.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It creates the following folders:

  • %Windows%\system\_sv_CMD_

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "userinit.exe,%Windows%\system\svchost.exe"

Propagation

This Worm creates the following folders in all removable drives:

  • {Removable Drive}\RECYCLER

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

  • {Removable Drive}\RECYCLER\INFO.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]
open=
shell\open\Command=RECYCLER\INFO.exe
shell\open\Default=1
shell\explore\Command=RECYCLER\INFO.exe

Other Details

This Worm does the following:

  • It adds the following entries to the global atom table to ensure that only one of its copies runs at any one time:
    • _U_is running
  • Executes the following command:
    • explorer.exe {Removable Drive}

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

5.883.00

FIRST VSAPI PATTERN DATE:

08 Apr 2009

VSAPI OPR PATTERN File:

5.884.00

VSAPI OPR PATTERN Date:

09 Apr 2009

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Identify and terminate files detected as WORM_SMALL.HYN

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. 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.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Userinit = "userinit.exe,%Windows%\system\svchost.exe"

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  
  • {Removable Drive}\RECYCLER
  • %Windows%\system\_sv_CMD_

Step 6

Search and delete this file

[ 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.
  • %Windows%\system\svchost.exe

Step 7

Search and delete AUTORUN.INF files created by WORM_SMALL.HYN that contain these strings

[ Learn More ]
DATA_GENERIC
  • If the lines are present, delete the file.
  • Repeat steps 3 to 6 for the remaining AUTORUN.INF files in other remaining removable drives.
  • Close Search Results.
  • *Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).

    For Windows Vista, Windows 7, Windows Server 2003, Windows 8, Windows 8.1, and Windows Server 2012:

    1. Open a Windows Explorer window.
      • For Windows Vista, 7, and Server 2008 users, click Start>Computer.
      • For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
    2. In the Search Computer/This PC input box, type:
      AUTORUN.INF
    3. Select the file, then open using Notepad.
    4. Check if the following lines are present in the file:
      DATA_GENERIC
    5. If the lines are present, delete the file.
    6. Repeat steps 3 to 5 for the remaining AUTORUN.INF files in other remaining removable drives.
    7. Close Search Results.

    Step 8

    Scan your computer with your Trend Micro product to delete files detected as WORM_SMALL.HYN. 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 the following Trend Micro Support pages for more information:


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