arrow_back
search
close

BKDR_DLLBOT.A

October 09, 2012
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • 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

File Size:

65,536 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

04 Oct 2011

Payload:

Compromises system security

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

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.472.04

FIRST VSAPI PATTERN DATE:

04 Oct 2011

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

[ Learn More ]

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

Step 3

Delete this registry value

[ Learn More ]

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}

Step 4

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result. %System%\oemblos.sig

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.


Did this description help? Tell us how we did.