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BKDR_BIFROSE.ZAS

October 08, 2012
 Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, XP, 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 opens random ports.

It opens a hidden Internet Explorer window.

  TECHNICAL DETAILS

File Size:

86,523 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

08 Sep 2010

Installation

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

  • %WINDOWS%\WinSxS\winsxs.exe

It drops the following files:

  • %WINDOWS%\WinSxS\wlog32
  • %User Application Data%\settings32.dat

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE

HKEY_CURRENT_USER\Software\winsxs32

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

Other Details

This backdoor opens a hidden Internet Explorer window.

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

07.460.06

VSAPI PATTERN Date:

13 Sep 2010

VSAPI PATTERN Date:

9/13/2010 12:00:00 AM

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

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.

%Windows%\WinSxS\wlog32
%Application Data%\settings32.dat

Step 3

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_CURRENT_USER\Software
    • winsxs32
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • winsxs32

Step 4

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