BKDR_DLLBOT.A
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This backdoor connects to a certain IP address.
Once connection is established, it may perform certain routines depending on the received command.
This backdoor may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.
TECHNICAL DETAILS
Arrival Details
This backdoor may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This backdoor drops the following files:
- %System%\w32timesvc.dll - also detected as BKDR_DLLBOT.A
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
It drops the following non-malicious files:
- %System%\oemblos.sig
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
Autostart Technique
This backdoor registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W32TimeApp\Parameters
ServiceDll = %System%\w32timesvc.dll
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W32TimeApp
ImagePath = %System%\svchost.exe -k W32TimeApp
Other System Modifications
This backdoor adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
W32TimeApp = {hex values}
NOTES:
It connects to the following IP address:
- {BLOCKED}.{BLOCKED}.77.46
Once connection is established, it may perform the following routines depending on the received command:
- download and execute file (downloaded file is saved as %User Temp%\{temp file name}.exe
- get drive information (drives, free space)
- get network information (IP, hostname, etc.)
- list/ search / delete files
- create / terminate process
- list processes
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Restart in Safe Mode, and then 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
- W32TimeApp
- W32TimeApp
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
- W32TimeApp = {hex values}
- W32TimeApp = {hex values}
Step 4
Search and delete this file
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_DLLBOT.A. 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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