WORM_AUTORUN.ACO

Malware type: Worm

Aliases: Worm.Win32.AutoIt.u (Kaspersky), W32.SillyFDC (Symantec), TR/Autoit.NAK (Avira), Mal/Generic-A (Sophos),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Medium

Distribution potential:

Medium

Infection Channel 1 : Propagates via removable drives


Infection Channel 2 : Copies itself in all available physical drives


Description: 

This worm may be dropped by other malware. It may be downloaded unknowingly by a user when visiting malicious Web sites.

It drops copies of itself.

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

It disables Task Manager. It does the said routine to avoid termination from the affected system's memory. It creates registry key(s)/entry(ies).

It propagates by dropping copies of itself into removable and physical drives.

For additional information about this threat, see:

Description created: Feb. 20, 2008 9:59:54 PM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 289,507 Bytes (compressed)

Initial samples received on: Feb 20, 2008

Compression type: UPX

Payload 1: Disables Task Manager

Details:

Arrival, Installation, and Autostart Technique

This worm may be dropped by other malware. It may be downloaded unknowingly by a user when visiting malicious Web site(s).

It drops the following copy(ies) of itself:

  • %System%\KHATARNAK.EXE
  • %Windows%\KHATARNAK.EXE
  • C:\Documents and Settings.exe
  • C:\Program Files.exe
  • C:\WINDOWS.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. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It creates the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Run
KHATARNAK Loader = "%System%\KHATARNAK.exe"

It modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\
CurrentVersion\Winlogon
Shell = "Explorer.exe KHATARNAK.exe"

(Note: The default value data for the said registry entry is Explorer.exe.)

Other System Modifications

This worm creates the following registry entry(ies) to disable Task Manager:

HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Policies\System
DisableTaskMgr = "1"

It creates the following registry key(s)/entry(ies):

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

Propagation via Physical/Removable Drives

This worm enumerates all drives in the system and drops copies of itself as any of the following file names:

  • Adventure Games.exe
  • Cool Stuff.exe
  • Documents.exe
  • Games.exe
  • Jokes.exe
  • Latest Songs.exe
  • New Folder.exe
  • Pics.exe
  • Pictures.exe
  • Secrets.exe
  • Softwares.exe
  • Songs.exe

Affected Platforms

This worm runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: John Amparado

Revision History:

First pattern file version: 5.120.05
First pattern file release date: Feb 21, 2008

SOLUTION


Minimum scan engine version needed: 8.300

Pattern file needed: 7.505.00

Pattern release date: Sep 30, 2010


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Identifying the Malware Files

  1. Scan your computer with your Trend Micro antivirus product.
  2. Note the path and file name of all files detected as WORM_AUTORUN.ACO.

Trend Micro customers need to download the latest virus pattern file before scanning their computer. Other users can use Housecall, the Trend Micro online threat scanner.

Terminating the Malware Process

Since this malware uses a file name that is also the file name of a legitimate process, it is necessary to use third party process viewers such as Process Explorer, to isolate the malware process itself.

If the process you are looking for is not in the list displayed by Process Explorer, proceed to the succeeding solution set.

  1. Download Process Explorer.
  2. Extract the contents of the compressed (ZIP) file to a location of your choice.
  3. Execute Process Explorer by double-clicking PROCEXP.EXE.
  4. In the Process Explorer window, locate the malware file(s) detected earlier.
  5. Right-click on the detected files, then click Kill Process Tree.
  6. Do the same for all detected malware files in the list of running processes.
  7. Close Process Explorer.

*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

If the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Removing/Restoring Autostart Entries from the Registry

This solution deletes/modifies registry keys/entries added/modified by this malware. Before performing the steps below, make sure you know how to back up the registry and how to restore it if a problem occurs. Refer to this Microsoft article for more information about modifying your computer's registry.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate the entry:
    Shell = "Explorer.exe KHATARNAK.exe"
  4. Right-click on the value name and choose Modify. Change the value data of this entry to:
    explorer.exe
  5. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>Run
  6. In the right panel, locate and delete the entry:
    KHATARNAK Loader = "%System%\KHATARNAK.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.)

Removing Other Added Entries from the Registry

  1. Still in Registry Editor, in the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>Windows>
    CurrentVersion>Policies>System
  2. In the right panel, locate and delete the following:
    DisableTaskMgr = "1"
  3. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>Windows>
    CurrentVersion>Policies>Explorer
  4. In the right panel, locate and delete the following:
    NofolderOptions = "1"
  5. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

Scan your computer with Trend Micro antivirus and delete files detected as WORM_AUTORUN.ACO. To do this, Trend Micro customers must download the latest virus pattern file and scan their computers. Other Internet users can use HouseCall, the Trend Micro online threat scanner.




Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.