TROJ_DLOADER.YJF
ERROR (Microsoft); Trojan Horse (Symantec); Trojan.Win32.Scar.dkaj (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Downloader.VB.BVM (AVG)
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.
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 creates the following folders:
- %Windows%\Crystal
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
Autostart Technique
This Trojan registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\stuad
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\htuad
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\htoad
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
RTR\TR
It adds the following registry entries:
HKEY_CURRENT_USER\Software\VB and VBA Program Settings\
RTR\TR
RT = ",,,,"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System Root%\\{malware file name}.exe = "{random characters}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
Description = "{random characters}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
Description = "Transaction Coordinator"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
ImagePath = "%Windows%\Crystal\smss.exe /service"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\stuad
Type = "11"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
Description = "{random characters}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
Description = "Transaction Coordinator"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
ImagePath = "%Windows%\msapps\csrss.exe /service"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htuad
Type = "11"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
Description = "{random characters}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
Description = "Transaction Coordinator"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
ImagePath = "svshost.exe /service"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\htoad
Type = "11"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control
ServicesPipeTimeout = "271"
Dropping Routine
This Trojan drops the following files:
- %System%\svshost
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
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 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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- stuad
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- htuad
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- htoad
- In HKEY_CURRENT_USER\Software\VB and VBA Program Settings\RTR
- TR
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\VB and VBA Program Settings\RTR\TR
- RT = ",,,,"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- %System Root%\{malware file name}.exe = "{random characters}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- Description = "{random characters}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- Description = "Transaction Coordinator"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- ErrorControl = "1"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- ImagePath = "%Windows%\Crystal\smss.exe /service"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- ObjectName = "LocalSystem"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\stuad
- Type = "11"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- Description = "{random characters}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- Description = "Transaction Coordinator"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- ErrorControl = "1"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- ImagePath = "%Windows%\msapps\csrss.exe /service"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- ObjectName = "LocalSystem"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htuad
- Type = "11"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- Description = "{random characters}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- Description = "Transaction Coordinator"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- ErrorControl = "1"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- ImagePath = "svshost.exe /service"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- ObjectName = "LocalSystem"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\htoad
- Type = "11"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control
- ServicesPipeTimeout = "271"
Step 5
Search and delete this file
- %System%\svshost
Step 6
Search and delete this folder
- %Windows%\Crystal
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DLOADER.YJF. 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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