WORM_MALAS.C

 Analysis by: Marfel Tiamzon

 ALIASES:

Trojan:Win32/Malex.gen!E (Microsoft); P2P-Worm.Win32.Malas.c (Kaspersky); W32/Malas-G (Sophos); W32/Bindo.worm (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm arrives by connecting affected removable drives to a system.

It adds registry entries to enable its automatic execution at every system startup.

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:

135,168 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

16 Jul 2009

Arrival Details

This worm arrives by connecting affected removable drives to a system.

Installation

This worm drops the following files:

  • %System Root%\Autorun.inf
  • %Windows%\Tasks\At1.job
  • %Windows%\Tasks\At2.job
  • %Start Menu%\Programs\Startup\Office Update.lnk

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %Start Menu% is the current user's Start Menu folder, which is usually C:\Windows\Profiles\{user name}\Start Menu on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu on Windows NT and C:\Windows\Start Menu or C:\Documents and Settings\{User name}\Start Menu on Windows 2000, XP, and Server 2003.)

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

  • %System Root%\autoply.exe
  • %Windows%\Web\OfficeUpdate.exe
  • %User Profile%\userinit.exe
  • %User Temp%\svchost.exe
  • %Program Files%\Common Files\Microsoft Shared\MSshare.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %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.. %Program Files% is the default Program Files folder, usually C:\Program Files.)

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
SoundMax = "%User Profile%\userinit.exe"

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
Nofolderoptions = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
Nofolderoptions = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
DisableConfig = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows NT\SystemRestore
DisableSR = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = "48"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "2"

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "2"

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
NextAtJobId = "2"

(Note: The default value data of the said registry entry is 1.)

Propagation

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

  • autoply.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.inf
[autorun]
action=Open Drive
open=autoply.exe OPEN
icon=C:\windows\system32\shell32.dll,8
shell\open=Open
shell\open\Command=autoply.exe OPEN
shell\open\Default=1
shell\explore=Explore
shell\explore\Command=autoply.exe EXPLORE
shell\AutoPlay=AutoPlay
shell\AutoPlay\Command=autoply.exe OPEN

NOTES:

This worm drops the following shortcut file in removable drives to point to this worm's copy in the removable drive:

  • New Folder.lnk

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

7.250.07

FIRST VSAPI PATTERN DATE:

16 Jul 2009

VSAPI OPR PATTERN File:

7.251.00

VSAPI OPR PATTERN Date:

16 Jul 2009

Step 1

For Windows ME and XP users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and terminate files detected as WORM_MALAS.C

[ Learn More ]
  1. For Windows 98 and ME users, 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 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
    • SoundMax = "%User Profile%\userinit.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Nofolderoptions = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Nofolderoptions = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\SystemRestore
    • DisableConfig = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\SystemRestore
    • DisableSR = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = "48"

Step 4

Restore this modified 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\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "2"
      To: HideFileExt = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "2"
      To: ShowSuperHidden = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • From: NextAtJobId = "2"
      To: NextAtJobId = "1"

Step 5

Search and delete these files

[ 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.
  • %System Root%\Autorun.inf
  • %Windows%\Tasks\At1.job
  • %Windows%\Tasks\At2.job
  • %Start Menu%\Programs\Startup\Office Update.lnk
  • {drive letter}\New Folder.lnk

Step 6

Search and delete AUTORUN.INF files created by WORM_MALAS.C that contain these strings

[ Learn More ]
autorun.inf
[autorun]
action=Open Drive
open=autoply.exe OPEN
icon=C:\windows\system32\shell32.dll,8
shell\open=Open
shell\open\Command=autoply.exe OPEN
shell\open\Default=1
shell\explore=Explore
shell\explore\Command=autoply.exe EXPLORE
shell\AutoPlay=AutoPlay
shell\AutoPlay\Command=autoply.exe OPEN

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_MALAS.C 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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