Threat Description

Trojan-Dropper: W32/Agent.FBB


Category: Malware
Type: Trojan-Dropper
Platform: W32
Aliases: Trojan-Dropper:W32/Agent.FBB, Trojan-Dropper.Win32.Agent.vmh


This type of trojan contains one or more malicious programs, which it will secretly install and execute.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

For further assistance, F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

Trojan-Dropper:W32/Agent.FBB appears to be an innocent EXE file, and is usually delivered as an e-mail attachment, or as a standalone file. The recipient must click on and execute the EXE file in order to infect their system.


On execution, Agent.FBB creates a copy of itself as %appdata%\deveinf.exe. A process iexplore.exe is created and two DLL files, devecl.dll and deveio.dll, are injected into it. The process name is the same as the process name for the legitimate application Microsoft Internet Explorer, and is deliberately used to camouflage the malware.The trojan also creates DLL files in the application data folder (by default, C:\Documents and Settings\[username]\Application Data) and the Windows folder (default is C:\Winnt for Windows NT/2000 and C:\Windows for Windows XP). One of the files created in the Windows folder, devekd.sys, uses rootkit techniques to hide itself, the injected process IEXPLORE.EXE, and the other malicious dll files.


The deveio.dll file injected into the iexplore.exe process is detected as Backdoor:W32/Hupigon.BXBH and is a keylogger program. Any information typed in by the individual on the infected system is logged. The malware author can then enter the infected system at their own leisure and retrieve the logged information using a separate server program.The other injected file devecl.dll is detected as Trojan:W32/Inject.EC and acts by manipulating the process to make registry changes. The changes to the winlogon registry keys enable the malware to start automatically whenever the system is restarted, while another registry key change allows the rootkit to start automatically as a Windows NT service on every subsequent startup. The changes also hide the Windows system file devenum.dll, which enumerates the available devices which receive DirectX data.

File System Changes

Creates these files:

  • %windir%\system32\devecl.dll
  • %windir%\system32\deveio.dll
  • %windir%\system32\drivers\devekd.sys
  • %appdata%\dever.tmp
Process Changes

Creates these mutexes:

  • deveinf.exe
Registry Modifications

Sets these values:

  • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSKDC Type = 00000001
  • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSKDC Start = 00000003
  • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSKDC ErrorControl = 00000000
  • HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSKDC ImagePath = C:\WINDOWS\System32\drivers\devekd.sys
  • HKEY_CURRENT_USER\Software\myclient Software = iamxxxx
  • HKEY_CURRENT_USER\Software\myclient myclient =
  • HKEY_CURRENT_USER\Software\myclient ip =
  • HKEY_CURRENT_USER\Software\myclient port = 000001BB
  • HKEY_CURRENT_USER\Software\Microsoft Waiting = 0100007F
  • HKEY_CURRENT_USER\Software\Windows NT\CurrentVersion\Winlogon Shell = explorer.exe C:\DOCUME~1\[username]\APPLIC~1\deveinf.exe


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