TROJ_DROPPE.YYXP
Windows 2000, Windows XP, Windows Server 2003
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 deletes itself after execution.
TECHNICAL DETAILS
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%\registry\registry.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:
- %User Temp%\registry
(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.)
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
registry = "%User Temp%\registry\registry.exe"
Other System Modifications
This Trojan modifies the following file(s):
- %Application Data%\GDIPFONTCACHEV1.DAT
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)
It deletes the following files:
- {malware path and file name}:zone.identifier
- %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.284.366531
- %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.284.366531
- %User Profile%\v2.0.50727.42\security.config.cch.284.366734
(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 modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
GDIPlus
FontCachePath = "%Application Data%"
(Note: The default value data of the said registry entry is %User Profile%\Local Settings\Application Data.)
Dropping Routine
This Trojan drops the following files:
- %User Temp%\bfb8945abf404b17b112b2954f89f3ab.exe
- %User Temp%\cb2bf267eb034ee3b63efd10d545de83.exe
- %System Root%\config\SteamAppData.vdf
- %User Temp%\950d9b29a4d74716b0f6b22aae3867cc.txt
- %User Temp%\636cbff402bc4ed5921a2e42ee4df79b.txt
(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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Other Details
This Trojan deletes itself after execution.
This report is generated via an automated analysis system.
SOLUTION
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 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
- registry = "%User Temp%\registry\registry.exe"
Step 4
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\GDIPlus
- From: FontCachePath = "%Application Data%"
To: FontCachePath = ""%User Profile%\Local Settings\Application Data""
- From: FontCachePath = "%Application Data%"
Step 5
Search and delete these components
- %User Temp%\bfb8945abf404b17b112b2954f89f3ab.exe
- %User Temp%\cb2bf267eb034ee3b63efd10d545de83.exe
- %System Root%\config\SteamAppData.vdf
- %User Temp%\950d9b29a4d74716b0f6b22aae3867cc.txt
- %User Temp%\636cbff402bc4ed5921a2e42ee4df79b.txt
Step 6
Search and delete this folder
- %User Temp%\registry
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DROPPE.YYXP. 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 deleted/modified files and/or registry entries from backup
*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- %Application Data%\GDIPFONTCACHEV1.DAT
Step 9
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.
- {malware path and file name}:zone.identifier
- %Windows%\Microsoft.NET\Framework\v2.0.50727\config\security.config.cch.284.366531
- %Windows%\Microsoft.NET\Framework\v2.0.50727\config\enterprisesec.config.cch.284.366531
- %User Profile%\v2.0.50727.42\security.config.cch.284.366734
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