Analysis by: Abraham Latimer Camba


Windows 2000, Windows XP, Windows Server 2003


  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes


Infection Channel:

Dropped by other malware

This backdoor may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system.

It logs a user's keystrokes to steal information.

It deletes the initially executed copy of itself.


File Size:

19,968 bytes

File Type:


Memory Resident:


Initial Samples Received Date:

27 Sep 2012


Steals information, Logs keystrokes, Collects system information

Arrival Details

This backdoor may be dropped by the following malware:


This backdoor drops the following copies of itself into the affected system:

  • %System%\tpframe.exe

(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 adds the following processes:

  • svchost.exe

It injects itself into the following processes as part of its memory residency routine:

  • svchost.exe

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

tpbar = "%System%\tpframe.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\



Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Perform remote shell commands
  • Read file and send content to C&C

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}g.{BLOCKED}s.net

It posts the following information to its command and control (C&C) server:

  • Computer name
  • User name

Information Theft

This backdoor logs a user's keystrokes to steal information.

Stolen Information

This backdoor saves the stolen information in the following file:

  • %User Temp%\~{hex string}.tmp

(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.)

Other Details

This backdoor deletes the initially executed copy of itself


It checks for the presence of the following processes:

  • 360tray.exe
  • avastui.exe
  • avguard.exe
  • avp.exe
  • ccsvchst.exe
  • mcagent.exe
  • op_mon.exe
  • pctstray.exe
  • v3ltray.exe
  • v3svc.exe
  • vsserv.exe

If the said processes are found in the system, it will not terminate itself and will not execute as intended.


Minimum Scan Engine:


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

Remove the malware/grayware file that dropped/downloaded BKDR_SHELL.ABG

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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\SOFTWARE\Microsoft\Windows\CurrentVersion\policies
    • Explorer
    • Local AppWizard-Generated Applications

Step 5

Search and delete these files

[ 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.
  • %User Temp%\~{hex string}.tmp

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_SHELL.ABG. 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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