BKDR_BEASTDOOR.B
Backdoor:Win32/Beastdoor.B (Microsoft); BackDoor-AMQ (McAfee); Backdoor.Beasty (Symantec); Backdoor.Win32.Beastdoor.kb (Kaspersky); BehavesLike.Win32.Malware.wsc (mx-v) (Sunbelt); Trojan horse BackDoor.Generic12.CIGR (AVG)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It disables Task Manager, Registry Editor, and Folder Options.
It deletes itself after execution.
TECHNICAL DETAILS
31,317 bytes
EXE
Yes
27 May 2013
Arrival Details
This backdoor 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 backdoor drops the following copies of itself into the affected system:
- %Windows%\kookjin.exe
- %System%\msttyh.com
- %Windows%\msagent\msjtdh.com
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}
StubPath = "%System%\msttyh.com"
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SAM\A
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
COM Service = "%Windows%\msagent\msjtdh.com"
It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
COM Service = "%Windows%\msagent\msjtdh.com"
Dropping Routine
This backdoor drops the following files:
- %System%\mslg.blf
- %Windows%\kookjin.exe
- %System%\msttyh.com
- %Windows%\msagent\msjtdh.com
Other Details
This backdoor deletes itself after execution.
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
Enable Registry Editor, Task Manager, and Folder options
Step 4
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\SAM
- A
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
- {42CE4021-DE03-E3CC-EA32-40BB12E6015D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
- Run
- In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
- Run
Step 5
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{42CE4021-DE03-E3CC-EA32-40BB12E6015D}
- StubPath = "%System%\msttyh.com"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
- COM Service = "%Windows%\msagent\msjtdh.com"
Step 6
Search and delete these components
- %System%\mslg.blf
- %Windows%\kookjin.exe
- %System%\msttyh.com
- %Windows%\msagent\msjtdh.com
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_BEASTDOOR.B. 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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