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WORM_AUTEX.A

Overview

Malware type: Worm

Aliases: Worm.Win32.Autex.a (Kaspersky), W32/Autex.worm (McAfee), W32.Autex.Worm (Symantec), Worm/Autex.A (Avira),

In the wild: No

Destructive: No

Language: English

Platform: Windows 95, 98, ME, NT, 2000, XP

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Medium

Distribution potential:

Medium

Description: 

This memory-resident worm enumerates drive letters and copies itself to these drives as AUTO.EXE. It disables the registry editing tool and sets the Internet Explorer startup page to point to a malicious Web site.

It also does several regisrtry modifications to enable itself to run every time Windows restarts, or whenever files with the following extensions are opened:

  • TXT
  • SWF
  • MP3
  • DLL
  • HTML

This malware is written in Visual Basic and runs on Windows 95, 98, ME, NT, 2000 and XP.

For additional information about this threat, see:

Description created: Nov. 18, 2003 12:44:32 AM GMT -0800


Technical Details

Size of malware: 147,973 Bytes

Initial samples received on: Nov 18, 2003

Details:

Arrival and Installation

This memory-resident worm enumerates drive letters and copies itself to these drives as AUTO.EXE. To run its copy on a remote system, the worm creates an AUTORUN.INF file using the command:

OPEN = auto.exe

The worm then, attempts to make copies of itself as follows:

  • %Program Files%\Auto.exe
  • %Windows%\Auto.exe
  • %Windows%\All Users\Desktop\Sysboy.exe
  • %Windows%\All Users\Start Menu\Programs\Auto.exe
  • %Windows%\Start Menu\Programs\Auto.exe
  • %Windows%\Desktop\Sysgril.exe

(Note: %Windows% is the default Windows folder, usually C:\Windows or C:\WINNT.)

Autostart Techniques

The malware creates the following registry entries in order for the malware copies to be executed every time Windows restarts:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Run
"Explorer"="<malware path>"
"Systry"="<malware path>"
"Systryt"="<malware path>"
"rundll32"="<malware path>"
"rundll64"="<malware path>"

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\RunServices
CurrentVersion\Run
"Explorer"="<malware path>"
"Systry"="<malware path>"
"Systryt"="<malware path>"
"rundll32"="<malware path>"
"rundll64"="<malware path>"

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Runonce
"Explorer"="<malware path>"
"Systry"="<malware path>"
"Systryt"="<malware path>"
"rundll32"="<malware path>"
"rundll64"="<malware path>"

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Runonceex
"Explorer"="<malware path>"
"Systry"="<malware path>"
"Systryt"="<malware path>"
"rundll32"="<malware path>"
"rundll64"="<malware path>"

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Runservicesonce
"Explorer"="<malware path>"
"Systry"="<malware path>"
"Systryt"="<malware path>"
"rundll32"="<malware path>"
"rundll64"="<malware path>"

Shell Spawning Technique

It also ensures its automatic execution whenever file with the extensions TXT, SWF, MP3, DLL and HTML are opened in Windows Explorer. It does this by creating the following registry entries:

HKEY_CLASSES_ROOT\txtfile\shell\open\command
[first home page = <malware path>:]

HKEY_CLASSES_ROOT\swffile\shell\open\command
[first home page = <malware path>:]

HKEY_CLASSES_ROOT\mp3file\shell\open\command
[first home page = <malware path>:]

HKEY_CLASSES_ROOT\dllfile\shell\open\command
[first home page = <malware path>:]

HKEY_CLASSES_ROOT\htmfile\shell\open\command
[first home page = <malware path>:]

Network Shares

Upon execution, it drops a copy of itself in all directories using a random name with a .EXE file extension and folder icon. It also drops a corresponding .HTML file, using the same file name of the dropped copy, to execute the worms copy.

Payload

The worm disables registry editing by creating the following registry entry:

HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Policies\System
[DiableRegistryTools]=[111]

It then sets the Internet Explorer startup page, so that it initially opens a malicious Web site, by adding this registry entry:

HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main
[Start Page] =[http:/ /xxxwwwjjj<BLOCKED>d.20forfree.com]

Other Registry Modifications

It also creates the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Policies\Explorer
[NoFolderOptions]=[111]

HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Policies\winoldapp
[norealmode]=[111]

Other Details

This worm is written in Visual Basic.




Analysis by: Brian Castro


Solution

Minimum scan engine version needed: 5.200

Pattern file needed: 1.685.07

Pattern release date: Nov 17, 2003


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 Program

Before proceeding to remove this malware, first identify the malware program.

Scan your system with Trend Micro antivirus and NOTE all files detected as WORM_AUTEX.A. To do this, Trend Micro customers must download the latest pattern file and scan their system. Other Internet users can use HouseCall, Trend Micro's free online virus scanner.

Terminating the Malware Program

This procedure terminates the running malware process from memory. You will need the name(s) of the file(s) detected earlier.

  1. Open Windows Task Manager.
    On Windows 95/98/ME systems, press
    CTRL+ALT+DELETE
    On Windows NT/2000/XP systems, press
    CTRL+SHIFT+ESC, then click the Processes tab.
  2. In the list of running programs*, locate the malware file or files detected earlier.
  3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your system.
  4. Do the same for all detected malware files in the list of running processes.
  5. To check if the malware process has been terminated, close Task Manager, and then open it again.
  6. Close Task Manager.

*NOTE: On systems running Windows 95/98/ME, Task Manager may not show certain processes. You may use a third party process viewer to terminate the malware process. Otherwise, continue with the next procedure, noting additional instructions.

Removing Autostart Entries from the Registry

Removing autostart entries from registry prevents the malware from executing during startup. This is also an effective way to terminate its process. In this procedure, you will need the name/s of the file/s detected earlier.

  1. Open Registry Editor. Click Start>Run, type Regedit then hit Enter.
  2. In the left panel, double click the following:
    HKEY_LOCAL_MACHINE>Software>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate and delete the entry or entries whose data value is the malware path and file name of the file/s detected earlier.
  4. Repeat this procedure for the following registry keys:

    HKEY_LOCAL_MACHINE>Software>Microsoft>
    Windows>RunServices
    HKEY_LOCAL_MACHINE>Software>Microsoft>
    Windows>Runonce
    HKEY_LOCAL_MACHINE>Software>Microsoft>
    Windows>Runonceex
    HKEY_LOCAL_MACHINE>Software>Microsoft>
    Windows>Runservicesonce
  5. Close Registry Editor.
NOTE: If you were not able to terminate the malware process from memory as described in the previous procedure, restart your system.

Addressing Registry Shell Spawning

Registry shell spawning executes the malware whenever a user opens files with EXE, PIF, COM, BAT, or HTA extensions. The following procedures should restore the registry to its original settings.

  1. Click Start>Run.
  2. In the Open input box, type:
    command /c copy %WinDir%\regedit.exe regedit.com | regedit.com
  3. Press Enter.
  4. In the left panel, double-click the following:
    HKEY_CLASSES_ROOT>txtfile>shell>open>command
  5. In the right panel, locate the registry entry:
    Default
  6. Check whether its value is the path and filename of the malware file.
  7. If the value is the malware file, right-click Default and select Modify to change its value.
  8. In the Value data input box, delete the existing value and type the default value:
    "notepad %1
  9. Again, in the left panel, double-click the following:
    HKEY_CLASSES_ROOT>swffile>shell>open>command
  10. In the right panel, locate the registry entry:
    Default
  11. Check whether its value is the path and filename of the malware file.
  12. If the value is the malware file, right-click Default and select Modify to change its value.
  13. In the Value data input box, delete the existing value and type the default value:
    "<path of your Macromedia flash player> %1
  14. Again, in the left panel, double-click the following:
    HKEY_CLASSES_ROOT> mp3file>shell>open>command
  15. In the right panel, locate the registry entry:
    Default
  16. Check whether its value is the path and filename of the malware file.
  17. If the value is the malware file, right-click Default and select Modify to change its value.
  18. In the Value data input box, delete the existing value and type the default value:
    " %1
  19. Again, in the left panel, double-click the following:
    HKEY_CLASSES_ROOT>dllfile>shell>open>command
  20. In the right panel, locate the registry entry:
    Default
  21. Check whether its value is the path and filename of the malware file.
  22. If the value is the malware file, right-click Default and select Modify to change its value.
  23. In the Value data input box, delete the subkey \shell\open\command
  24. Again, in the left panel, double-click the following:
    HKEY_CLASSES_ROOT>htmlfile>shell>open>command
  25. In the right panel, locate the registry entry:
    Default
  26. Check whether its value is the path and filename of the malware file.
  27. If the value is the malware file, right-click Default and select Modify to change its value.
  28. In the Value data input box, delete the existing value and type the default value:
    " %1
  29. Close Registry Editor.
  30. Click Start>Run, then type:
    command /c del regedit.com
  31. Press Enter.

Additional Windows ME/XP Cleaning Instructions

Running Trend Micro Antivirus

Scan your system with Trend Micro antivirus and delete all files detected as WORM_AUTEX.A. To do this, Trend Micro customers must download the latest pattern file and scan their system. Other Internet users can use HouseCall, Trend Micros free online virus scanner.


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