Modified by: Nikko Tamana
ALIASES:

TrojanDownloader:Win32/Obvod.M (Microsoft)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

  TECHNICAL DETAILS

File Size: 211,614 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 28 Oct 2013

Arrival Details

This Trojan 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 Trojan drops the following file(s)/component(s):

  • %User Temp%\abe4_appcompat.txt
  • %All Users Profile%\Application Data\{random file name 2}.dat
  • %Windows%\Tasks\At{1-240}.job

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.. %Windows% is the Windows folder, which is usually C:\Windows.)

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

  • %Windows%\Fonts\{random file name 1}.com
  • %System%\ctfmon.exe
  • %Program Files%\VMware\VMware Tools\VMwareTray.exe
  • %Program Files%\VMware\VMware Tools\VMwareUser.exe
  • %All Users Profile%\Application Data\{random file name 1}.exe

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
DisableScriptDebuggerIE = "yes"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Error Dlg Displayed On Every Error = "no"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
NoProtectedModeBanner = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
WarnOnZoneCrossing = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
2500 = "3"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Direct3D
LA = "261"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager
PendingFileRenameOperations = "@\??\%System%\@%System%\ctfmon.exe.tmp"

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

NOTES:

It renames the following original file names:

  • %Program Files%\VMware\VMware Tools\VMwareTray.exe
  • %Program Files%\VMware\VMware Tools\VMwareUser.exe
  • %System%\ctfmon.exe

To the following file names:

  • %Program Files%\VMware\VMware Tools\VMwareTray .exe
  • %Program Files%\VMware\VMware Tools\VMwareUser .exe
  • %System%\ctfmon .exe

It creates each schedule tasks (.job files) with file names %Windows%\Tasks\At1.job up to %Windows%\Tasks\At240.job

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.370.04
FIRST VSAPI PATTERN DATE: 28 Oct 2013
VSAPI OPR PATTERN File: 10.371.00
VSAPI OPR PATTERN Date: 29 Oct 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

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\Internet Explorer\Main
    • DisableScriptDebuggerIE = "yes"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Error Dlg Displayed On Every Error = "no"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • NoProtectedModeBanner = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • WarnOnZoneCrossing = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • 2500 = "3"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Direct3D
    • LA = "261"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager
    • PendingFileRenameOperations = "@\??\%System%\@%System%\ctfmon.exe.tmp"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = "48"

Step 4

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.
  • %User Temp%\abe4_appcompat.txt
  • %All Users Profile%\Application Data\{random file name 2}.dat
  • %Windows%\Tasks\At{1-240}.job

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_OBVOD.AT. 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.

NOTES:

Rename the following:

  • %Program Files%\VMware\VMware Tools\VMwareTray .exe
  • %Program Files%\VMware\VMware Tools\VMwareUser .exe
  • %System%\ctfmon .exe

To:

  • %Program Files%\VMware\VMware Tools\VMwareTray.exe
  • %Program Files%\VMware\VMware Tools\VMwareUser.exe
  • %System%\ctfmon.exe


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