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TROJ_DROPPE.ANH

February 14, 2014
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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.

  TECHNICAL DETAILS

File Size:

163,328 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Feb 2014

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 copies of itself into the affected system:

  • %User Temp%\ASI.exe

(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.)

It creates the following folders:

  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\Microsoft\CLR Security Config
  • %User Profile%\CLR Security Config\v2.0.50727.42

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
4ac688bf4283cbeddcff6e4ce8c9e606 = "%User Temp%\ASI.exe .."

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
4ac688bf4283cbeddcff6e4ce8c9e606 = "%User Temp%\ASI.exe .."

Other System Modifications

This Trojan deletes the following files:

  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.636.548984
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.636.548984
  • %User Profile%\v2.0.50727.42\security.config.cch.636.549125

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\4ac688bf4283cbeddcff6e4ce8c9e606

It adds the following registry entries:

HKEY_CURRENT_USER\Software\4ac688bf4283cbeddcff6e4ce8c9e606
US = "!"

HKEY_CURRENT_USER\Environment
SEE_MASK_NOZONECHECKS = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Temp%\ASI.exe = "%User Temp%\ASI.exe:*:Enabled:ASI.exe"

Dropping Routine

This Trojan drops the following files:

  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.new
  • %User Profile%\v2.0.50727.42\security.config.cch.new
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.new
  • %System Root%\.tmp
  • %User Startup%\4ac688bf4283cbeddcff6e4ce8c9e606.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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 key

[ 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
    • 4ac688bf4283cbeddcff6e4ce8c9e606

Step 4

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
    • 4ac688bf4283cbeddcff6e4ce8c9e606 = "%User Temp%\ASI.exe .."
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • 4ac688bf4283cbeddcff6e4ce8c9e606 = "%User Temp%\ASI.exe .."
  • In HKEY_CURRENT_USER\Software\4ac688bf4283cbeddcff6e4ce8c9e606
    • US = "!"
  • In HKEY_CURRENT_USER\Environment
    • SEE_MASK_NOZONECHECKS = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %User Temp%\ASI.exe = "%User Temp%\ASI.exe:*:Enabled:ASI.exe"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.new
  • %User Profile%\v2.0.50727.42\security.config.cch.new
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.new
  • %System Root%\.tmp
  • %User Startup%\4ac688bf4283cbeddcff6e4ce8c9e606.exe

Step 6

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\Microsoft\CLR Security Config
  • %User Profile%\CLR Security Config\v2.0.50727.42

Step 7

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

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.636.548984
  • %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.636.548984
  • %User Profile%\v2.0.50727.42\security.config.cch.636.549125


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