TROJ_DROPPE.ANH
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
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
163,328 bytes
EXE
Yes
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
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
Step 3
Delete this registry key
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
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
- %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
- %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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