WORM_DOORCAR.VI


 ALIASES:

Backdoor.Unpdoor (Symantec); Backdoor:MSIL/Pontoeb.B (Microsoft); Mal/MSIL-A (Sophos)

 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

This worm performs commands from a remote malicious user.

It also terminates itself if it is running under a Debugger or an Emulator. It also checks if the affected system uses certain display adapters.

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.

  TECHNICAL DETAILS

File Size:

104,960 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 May 2011

Payload:

Compromises system security

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:

  • %User Profile%\Application Data\Realhost.exe
  • %System%\host.exe

(Note: %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.. %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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • mnUXsx75Xusnv

It terminates itself if it finds the following processes in the affected system's memory:

  • CAIN
  • FILEMON
  • NETMON
  • NETSTAT
  • PROCMON
  • REGMON
  • TCPVIEW
  • WIRESHARK

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows PC Driver = %User Profile%\Application Data\Realhost.exe

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Windows-Network = %System%\host.exe

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
EnableBalloonTips = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0

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.)

Backdoor Routine

This worm connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}n.pf-control.de/bot/gate.php

NOTES:

It may perform the following commands from a remote malicious user:

  • Connects to malicious sites to download files/update of itself
  • Launches the following attacks:
    HTTP flood
    ICMP flood
    SYN flood
    UDP flood
  • Propagates itself in network and removable drives by attaching itself to archives with .RAR and .ZIP extension names

It also terminates itself if it is running under a Debugger or an Emulator. It also checks if the affected system uses any of the following display adapters:

  • Parallels Video Adapter
  • S3 Trio32/64
  • VirtualBox Graphics Adapter
  • VM Additions S3 Trio32/64
  • VMware SVGA II

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.180.14

FIRST VSAPI PATTERN DATE:

25 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

Identify and terminate files detected as WORM_DOORCAR.VI

[ Learn More ]
  1. 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.
  2. 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows PC Driver = %User Profile%\Application Data\Realhost.exe
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows-Network = %System%\host.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • EnableBalloonTips = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = 0
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = 0

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: 1

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_DOORCAR.VI. 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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