Analysis by: Sabrina Lei Sioting
 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

Upon execution, this worm drops files on the affected system.

This worm 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: 1,547,231 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 09 May 2011
Payload: Drops files

Installation

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

  • %System%\XP-D41D8CD9.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.)

It drops the following files:

  • %User Temp%\E_4\com.run
  • %User Temp%\E_4\dp1.fne
  • %System%\com.run
  • %System%\dp1.fne

(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.. %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 non-malicious files:

  • %System%\og.dll
  • %System%\og.edt
  • %System%\ul.dll

(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 creates the following folders:

  • %User Temp%\E_4

(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\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{OS version}-D41D8CD9 = %System%\{OS version}-D41D8CD9.EXE

It drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\¡¡¡¡¡¡.lnk

(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:

  • Recycled.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=Recycled.exe
shell\1=´ò¿ª(&O)
shell\1\Command=Recycled.exe
shell\2\=ä¯ÀÀ(&B)
shell\2\Command=Recycled.exe
shellexecute=Recycled.exe

Dropping Routine

This worm drops the following files:

  • %User Temp%\E_4\eAPI.fne - detected by Trend Micro as WORM_AUTORUN.CLX
  • %User Temp%\E_4\internet.fne - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %User Temp%\E_4\krnln.fnr - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %User Temp%\E_4\RegEx.fnr - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %User Temp%\E_4\shell.fne - detected by Trend Micro as WORM_AUTORUN.IJB
  • %User Temp%\E_4\spec.fne - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %System%\eAPI.fne - detected by Trend Micro as WORM_AUTORUN.CLX
  • %System%\internet.fne - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %System%\krnln.fnr - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %System%\RegEx.fnr - detected by Trend Micro as TROJ_PIDIEF.PUA
  • %System%\shell.fne - detected by Trend Micro as WORM_AUTORUN.IJB
  • %System%\spec.fne - detected by Trend Micro as TROJ_PIDIEF.PUA

(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.. %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.)

NOTES:

The dropped AUTORUN.INF is detected by Trend Micro as Mal_Otorun1

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.146.05
FIRST VSAPI PATTERN DATE: 09 May 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_FLYSTUD.AMF

     Mal_Otorun1
    TROJ_PIDIEF.PUA
    WORM_AUTORUN.CLX
    WORM_AUTORUN.IJB

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\CurrentVersion\Run
    • {OS version}-D41D8CD9 = "%System%\{OS version}-D41D8CD9.EXE"
>

Step 4

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. %User Temp%\E_4

Step 5

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 Startup%\¡¡¡¡¡¡.lnk
%System%\com.run
%System%\dp1.fne
%System%\og.dll
%System%\og.edt
%System%\ul.dll

Step 6

Search and delete AUTORUN.INF files created by WORM_FLYSTUD.AMF that contain these strings

[ Learn More ]
[AutoRun]
open=Recycled.exe
shell\1=´ò¿ª(&O)
shell\1\Command=Recycled.exe
shell\2\=ä¯ÀÀ(&B)
shell\2\Command=Recycled.exe
shellexecute=Recycled.exe

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_FLYSTUD.AMF. 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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