Backdoor:Win32/Agent.FV (Microsoft); [000012a8.EXE] (McAfee); Backdoor.Trojan (Symantec); Backdoor.Win32.Agent.ansn (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)


Windows 2000, Windows XP, Windows Server 2003


  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes


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 deletes itself after execution.


File Size: 59,904 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 07 Oct 2012

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.

Other System Modifications

This backdoor deletes the following files:

  • %Windows%\SoftwareDistribution\DataStore\Logs\edbtmp.log

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It modifies the following registry entries:

ServiceDll = "%System%\RvmwtdC.dll"

(Note: The default value data of the said registry entry is {random values}.)

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\39078_res.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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other Details

This backdoor deletes itself after execution.

This report is generated via an automated analysis system.


Minimum Scan Engine: 9.200

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

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\BITS\Parameters
    • From: ServiceDll = "%System%\RvmwtdC.dll"
      To: ServiceDll = ""{random values}""

Step 3

Search and delete this file

[ Learn More ]
There may be some 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%\39078_res.tmp

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_BIFROSE.SMK. 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.

Step 5

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %Windows%\SoftwareDistribution\DataStore\Logs\edbtmp.log

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